azure-cli-core breaking change detection

[tjprescott]

We have had instances where a change in azure-cli-core was not identified as a breaking change during development or code review, resulting in inadvertently breaking extensions or other interfacing tools. We should follow the example of the Python SDK to detect breaking changes to specific interfaces we want to ensure continue to work. Example files:

https://github.com/Azure/azure-sdk-for-python/blob/master/azure-sdk-tools/packaging_tools/code_report.py

https://github.com/Azure/azure-sdk-for-python/blob/master/azure-sdk-tools/packaging_tools/change_log.py

[tjprescott]

Also, our static analyzers (PEP8, pylint) will encourage us to make breaking changes without realizing it. See #8012.

[adewaleo]

Also see: https://github.com/Azure/azure-sdk-for-python/wiki/Automatic-ChangeLog

[adewaleo]

Will continue work on this in sprint 56 based on feedback from brainstorm meeting.

Update:
Moved to sprint 61 (post build) to allow for work on "compute" and "az feedback"