Create AMQP Management APIs; significant cleanup of Impl types to remove reference values.

[LarryOsterman]

Added initial support for AMQP Management APIs.

Initial support for AMQP management APIs.

Bonus changes:

1. Impl types no longer reference non-Impl types
2. Impl types now use RAII wrappers around uAMQP types.
3. Removed connectionToPoll parameter from most APIs.
4. Renamed Message to AmqpMessage to reduce possible type confusion.
5. Added the ability to detect empty messages.
6. Removed interop methods from MessageHeader, MessageProperties, and AmqpMessage in favor of factory methods which do the same.
7. Significant cleanup of MockAmqpServer test server to enable more flexibility.
8. Yield during polling loops to reduce CPU overhead.
9. Removed CreateChar and GetChar in favor of char32_t type.

Fixes #4549

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