Add 'azdev format'

[dciborow]

Add azdev format to auto format code using black.

This automatically fixes issues like incorrect spacing for users and reduces time spent fixing issues found from azdev linter and azdev style.

[wangzelin007]

I have some questions:

1. Can black automatically fix all problems detected by azdev linter and azdev style?
2. If it fixes some of the problems, what problems does it fix?
3. If user use CodeGen tool to autogenerated cli and extensions code,  will black automatic change the format of autogenerated code?
   I think these codes does not need to be adjusted.

[dciborow]

I have some questions:

1. Can black automatically fix all problems detected by azdev linter and azdev style?
2. If it fixes some of the problems, what problems does it fix?
3. If user use CodeGen tool to autogenerated cli and extensions code,  will black automatic change the format of autogenerated code?
   I think these codes does not need to be adjusted.

I think it will fix ALL flake8 issues, and easy pylint issues. It won't fix something like "using private method", but it does fix things like "trailing whitespace".

Black can be configured to exclude directories. I will look into reusing the pylintrc config to try and do this. https://github.com/psf/black#configuration