Iterate package (elastic#4473)

Improves package generation.

- Splits metrics data stream into app metrics, internal and profiles. This is following the indexing strategy proposal.  - Adds the dataset property to the manifest files so the right templates are created.
- Sort and dedup fields (within each yml file). Fields are now flattened.
- Generates data stream pipelines out of our definitions.json file

docs/fields.asciidoc

@@ -14441,16 +14441,6 @@ type: keyword
 Kubernetes node name
 
 
-type: keyword
-
---
-
-*`kubernetes.node.hostname`*::
-+
---
-Kubernetes hostname as reported by the node’s kernel
-
-
 type: keyword
 
 --