Fix header hierarchy for the API docs (Qiskit#1283)

The PR adds a method to autogenerate the correct level for the headers
of the MDX components (Attribute, Function, and Class) and regenerates
the API docs.

### How to find the heading level

Before setting the header, the script looks for the level of the
previous header to determine which one corresponds to the component that
is being generated. The script looks at all the siblings of the
`Cheerio` element we use to define the component to find the previous
header that wasn't created by the script before. We need to skip the
generated headers to avoid the case where we have multiple
methods/attributes/classes at the same level which shouldn't be mixed
with the header of the previous level.

If there's no header found in the first step, it means that we are
dealing with a component inside of an inline class, and therefore, the
script searches for the last header that corresponds to an inline class
to determine the new level. This is true because when we are inside an
inline class, there are no headers that haven't been generated by the
script.

Notice that the script always sets the header of an inline class in the
parent level instead of creating another sibling, so we cannot search
for generated siblings' headers.

To distinguish between the headers of the different components, an
attribute called `data-header-type` is used. This attribute is useful in
the last search.

Closes Qiskit#1215

---------

Co-authored-by: Eric Arellano <14852634+Eric-Arellano@users.noreply.github.com>

docs/api/qiskit-ibm-provider/0.10/ibm_utils.mdx

@@ -42,6 +42,8 @@ Utility functions related to the IBM Quantum Provider.
 
 Message broker for the Publisher / Subscriber mechanism
 
+### Publisher
+
 <Class id="qiskit_ibm_provider.utils.pubsub.Publisher" github="https://github.com/Qiskit/qiskit-ibm-provider/tree/stable/0.10/qiskit_ibm_provider/utils/pubsub.py#L140-L155" signature="Publisher">
   Represents a “publisher”.
 
@@ -51,7 +53,7 @@ Message broker for the Publisher / Subscriber mechanism
   Publisher().publish("event", args, ... )
   ```
 
-  ### publish
+  #### publish
 
   <Function id="qiskit_ibm_provider.utils.pubsub.Publisher.publish" github="https://github.com/Qiskit/qiskit-ibm-provider/tree/stable/0.10/qiskit_ibm_provider/utils/pubsub.py#L152-L155" signature="publish(event, *args, **kwargs)">
     Triggers an event, and associates some data to it, so if there are any subscribers, their callback will be called synchronously.
@@ -62,12 +64,14 @@ Message broker for the Publisher / Subscriber mechanism
   </Function>
 </Class>
 
+### Subscriber
+
 <Class id="qiskit_ibm_provider.utils.pubsub.Subscriber" github="https://github.com/Qiskit/qiskit-ibm-provider/tree/stable/0.10/qiskit_ibm_provider/utils/pubsub.py#L158-L182" signature="Subscriber">
   Represents a “subscriber”.
 
   Every component (class) can become a [`Subscriber`](#qiskit_ibm_provider.utils.pubsub.Subscriber "qiskit_ibm_provider.utils.pubsub.Subscriber") and subscribe to events, that will call callback functions when they are emitted.
 
-  ### clear
+  #### clear
 
   <Function id="qiskit_ibm_provider.utils.pubsub.Subscriber.clear" github="https://github.com/Qiskit/qiskit-ibm-provider/tree/stable/0.10/qiskit_ibm_provider/utils/pubsub.py#L180-L182" signature="clear()">
     Unsubscribe everything
@@ -77,7 +81,7 @@ Message broker for the Publisher / Subscriber mechanism
     `None`
   </Function>
 
-  ### subscribe
+  #### subscribe
 
   <Function id="qiskit_ibm_provider.utils.pubsub.Subscriber.subscribe" github="https://github.com/Qiskit/qiskit-ibm-provider/tree/stable/0.10/qiskit_ibm_provider/utils/pubsub.py#L168-L173" signature="subscribe(event, callback)">
     Subscribes to an event, associating a callback function to that event, so when the event occurs, the callback will be called.
@@ -89,7 +93,7 @@ Message broker for the Publisher / Subscriber mechanism
     `bool`
   </Function>
 
-  ### unsubscribe
+  #### unsubscribe
 
   <Function id="qiskit_ibm_provider.utils.pubsub.Subscriber.unsubscribe" github="https://github.com/Qiskit/qiskit-ibm-provider/tree/stable/0.10/qiskit_ibm_provider/utils/pubsub.py#L175-L178" signature="unsubscribe(event, callback)">
     Unsubscribe a pair event-callback, so the callback will not be called anymore when the event occurs.

docs/api/qiskit-ibm-provider/0.9/ibm_utils.mdx

@@ -42,6 +42,8 @@ Utility functions related to the IBM Quantum Provider.
 
 Message broker for the Publisher / Subscriber mechanism
 
+### Publisher
+
 <Class id="qiskit_ibm_provider.utils.pubsub.Publisher" github="https://github.com/qiskit/qiskit-ibm-provider/tree/stable/0.9/qiskit_ibm_provider/utils/pubsub.py" signature="Publisher">
   Represents a “publisher”.
 
@@ -51,7 +53,7 @@ Message broker for the Publisher / Subscriber mechanism
   Publisher().publish("event", args, ... )
   ```
 
-  ### publish
+  #### publish
 
   <Function id="qiskit_ibm_provider.utils.pubsub.Publisher.publish" signature="publish(event, *args, **kwargs)">
     Triggers an event, and associates some data to it, so if there are any subscribers, their callback will be called synchronously.
@@ -62,12 +64,14 @@ Message broker for the Publisher / Subscriber mechanism
   </Function>
 </Class>
 
+### Subscriber
+
 <Class id="qiskit_ibm_provider.utils.pubsub.Subscriber" github="https://github.com/qiskit/qiskit-ibm-provider/tree/stable/0.9/qiskit_ibm_provider/utils/pubsub.py" signature="Subscriber">
   Represents a “subscriber”.
 
   Every component (class) can become a [`Subscriber`](#qiskit_ibm_provider.utils.pubsub.Subscriber "qiskit_ibm_provider.utils.pubsub.Subscriber") and subscribe to events, that will call callback functions when they are emitted.
 
-  ### clear
+  #### clear
 
   <Function id="qiskit_ibm_provider.utils.pubsub.Subscriber.clear" signature="clear()">
     Unsubscribe everything
@@ -77,7 +81,7 @@ Message broker for the Publisher / Subscriber mechanism
     `None`
   </Function>
 
-  ### subscribe
+  #### subscribe
 
   <Function id="qiskit_ibm_provider.utils.pubsub.Subscriber.subscribe" signature="subscribe(event, callback)">
     Subscribes to an event, associating a callback function to that event, so when the event occurs, the callback will be called.
@@ -89,7 +93,7 @@ Message broker for the Publisher / Subscriber mechanism
     `bool`
   </Function>
 
-  ### unsubscribe
+  #### unsubscribe
 
   <Function id="qiskit_ibm_provider.utils.pubsub.Subscriber.unsubscribe" signature="unsubscribe(event, callback)">
     Unsubscribe a pair event-callback, so the callback will not be called anymore when the event occurs.

docs/api/qiskit-ibm-provider/ibm_utils.mdx

@@ -42,6 +42,8 @@ Utility functions related to the IBM Quantum Provider.
 
 Message broker for the Publisher / Subscriber mechanism
 
+### Publisher
+
 <Class id="qiskit_ibm_provider.utils.pubsub.Publisher" github="https://github.com/Qiskit/qiskit-ibm-provider/tree/stable/0.11/qiskit_ibm_provider/utils/pubsub.py#L140-L155" signature="Publisher">
   Represents a “publisher”.
 
@@ -51,7 +53,7 @@ Message broker for the Publisher / Subscriber mechanism
   Publisher().publish("event", args, ... )
   ```
 
-  ### publish
+  #### publish
 
   <Function id="qiskit_ibm_provider.utils.pubsub.Publisher.publish" github="https://github.com/Qiskit/qiskit-ibm-provider/tree/stable/0.11/qiskit_ibm_provider/utils/pubsub.py#L152-L155" signature="publish(event, *args, **kwargs)">
     Triggers an event, and associates some data to it, so if there are any subscribers, their callback will be called synchronously.
@@ -62,12 +64,14 @@ Message broker for the Publisher / Subscriber mechanism
   </Function>
 </Class>
 
+### Subscriber
+
 <Class id="qiskit_ibm_provider.utils.pubsub.Subscriber" github="https://github.com/Qiskit/qiskit-ibm-provider/tree/stable/0.11/qiskit_ibm_provider/utils/pubsub.py#L158-L182" signature="Subscriber">
   Represents a “subscriber”.
 
   Every component (class) can become a [`Subscriber`](#qiskit_ibm_provider.utils.pubsub.Subscriber "qiskit_ibm_provider.utils.pubsub.Subscriber") and subscribe to events, that will call callback functions when they are emitted.
 
-  ### clear
+  #### clear
 
   <Function id="qiskit_ibm_provider.utils.pubsub.Subscriber.clear" github="https://github.com/Qiskit/qiskit-ibm-provider/tree/stable/0.11/qiskit_ibm_provider/utils/pubsub.py#L180-L182" signature="clear()">
     Unsubscribe everything
@@ -77,7 +81,7 @@ Message broker for the Publisher / Subscriber mechanism
     `None`
   </Function>
 
-  ### subscribe
+  #### subscribe
 
   <Function id="qiskit_ibm_provider.utils.pubsub.Subscriber.subscribe" github="https://github.com/Qiskit/qiskit-ibm-provider/tree/stable/0.11/qiskit_ibm_provider/utils/pubsub.py#L168-L173" signature="subscribe(event, callback)">
     Subscribes to an event, associating a callback function to that event, so when the event occurs, the callback will be called.
@@ -89,7 +93,7 @@ Message broker for the Publisher / Subscriber mechanism
     `bool`
   </Function>
 
-  ### unsubscribe
+  #### unsubscribe
 
   <Function id="qiskit_ibm_provider.utils.pubsub.Subscriber.unsubscribe" github="https://github.com/Qiskit/qiskit-ibm-provider/tree/stable/0.11/qiskit_ibm_provider/utils/pubsub.py#L175-L178" signature="unsubscribe(event, callback)">
     Unsubscribe a pair event-callback, so the callback will not be called anymore when the event occurs.

docs/api/qiskit/0.19/logging.mdx

@@ -22,6 +22,8 @@ python_api_name: qiskit.ignis.logging
 | [`IgnisLogging`](qiskit.ignis.logging.IgnisLogging "qiskit.ignis.logging.IgnisLogging")()            | Singleton class to configure file logging via IgnisLogger |
 | [`IgnisLogReader`](qiskit.ignis.logging.IgnisLogReader "qiskit.ignis.logging.IgnisLogReader")()      | Class to read from Ignis log files                        |
 
+###
+
 <Class github="https://github.com/qiskit-community/qiskit-ignis/tree/stable/0.3/qiskit/ignis/logging/ignis_logging.py" signature="IgnisLogger(name, level=0)">
   A logger class for Ignis
 

docs/api/qiskit/0.19/qiskit.optimization.applications.ising.tsp.mdx

@@ -30,42 +30,44 @@ Convert symmetric TSP instances into Pauli list Deal with TSPLIB format. It supp
 | ------------------------------------------------------------------------------------------------------------------------------------------ | --------------------------------------------------- |
 | [`TspData`](#qiskit.optimization.applications.ising.tsp.TspData "qiskit.optimization.applications.ising.tsp.TspData")(name, dim, coord, w) | Create new instance of TspData(name, dim, coord, w) |
 
+### TspData
+
 <Class id="qiskit.optimization.applications.ising.tsp.TspData" signature="TspData(name, dim, coord, w)">
   Create new instance of TspData(name, dim, coord, w)
 
-  ### coord
+  #### coord
 
   <Attribute id="qiskit.optimization.applications.ising.tsp.TspData.coord">
     Alias for field number 2
   </Attribute>
 
-  ### count
+  #### count
 
   <Function id="qiskit.optimization.applications.ising.tsp.TspData.count" signature="count(value, /)">
     Return number of occurrences of value.
   </Function>
 
-  ### dim
+  #### dim
 
   <Attribute id="qiskit.optimization.applications.ising.tsp.TspData.dim">
     Alias for field number 1
   </Attribute>
 
-  ### index
+  #### index
 
   <Function id="qiskit.optimization.applications.ising.tsp.TspData.index" signature="index(value, start=0, stop=9223372036854775807, /)">
     Return first index of value.
 
     Raises ValueError if the value is not present.
   </Function>
 
-  ### name
+  #### name
 
   <Attribute id="qiskit.optimization.applications.ising.tsp.TspData.name">
     Alias for field number 0
   </Attribute>
 
-  ### w
+  #### w
 
   <Attribute id="qiskit.optimization.applications.ising.tsp.TspData.w">
     Alias for field number 3