[SB] Update API type hints for methods that accept dicts

[swathipil]

Complete after : #14807

In the above PR, changes were made to SB so that dict representations of the following objects are
now accepted and can be sent:

• ServiceBusMessage
• QueueProperties
• TopicProperties
• SubscriptionProperties
• RuleProperties

The API type hints that now accept dict representations of these objects should be updated to reflect the change. The type hint should show that an object of type typing.Mapping is accepted, NOT AN OBJECT OF TYPE Dict. Discussion for this update here: https://github.com/Azure/azure-sdk-for-python/pull/14807/files#r579153824.

The type hints for the following methods should be updated:

• _from_list in message.py
• add_message in message.py
• schedule_messages in _servicebus_sender.py
• send_messages in _servicebus_sender.py
• schedule_messages in _servicebus_sender_async.py
• send_messages in _servicebus_sender_async.py
• update_queue, update_topic, update_subscription, update_rule in management/_management_client.py
• • update_queue, update_topic, update_subscription, update_rule in aio/management/_management_client_async.py

[swathipil]

need to update all the isinstance(x, dict) to some sort of validation that the dict is of type Mapping and conforms to the Mapping protocol. Below is a prototype of that check from Anna:

def _check_instance(input):
    if isinstance(input, ServiceBusMessage):
        return True
    try:
        dict_message = dict(intput)
        dict['body]  # Check that a required key is present
        return True
    except (ValueError, TypeError, KeyError):
        raise ValueError("Message must be an instance of ServiceBusMessage or Mapping")
    return False

• add a test to check non-SBMessage-non-Mappable inputs raises an error as expected

[swathipil]

Merged: #17080