Add a new linter to run black on python files, and start applying it to some files. Remove these files from autopep8. The end goal is to entirely remove autopep8.

Some doc about black:

• https://black.readthedocs.io/en/stable/
• code style: https://black.readthedocs.io/en/stable/the_black_code_style/current_style.html
• stability policy: https://black.readthedocs.io/en/stable/the_black_code_style/#stability-policy

The --experimental-string-processing makes black split long strings into multiple lines. This seems important to me as not setting it would do the opposite: put the strings we already split back on a single line.

The flake8 E203 error code is incompatible with black, and not PEP8 compliant, so exclude it.

arc lint -- test/functional

test/functional/test_runner.py abc-*