Add python autoformatter

[mx-psi]

What does this PR do?

• Add black as pre-commit hook
• Add black to CircleCI
• Apply black to existing files

Motivation

• Enforce readability
• Reduce merge conflicts
• (Almost) consistent code style with integrations repos

Additional Notes

• Configuration mostly follows that of Add style checker and formatter integrations-core#3299
• black includes safety checks to verify no AST changes, so feel free to rely on the pipeline passing for reviewing
• If you still want to review, it is best reviewed hiding whitespace changes

How to merge this changes to your branch

This PR will likely provoke merge conflicts with existing PRs that modify .py files.
To help with this, do the following:

1. Cherry-pick da5c846
2. Install pre-commit (pip install pre-commit) and activate it (pre-commit install --install-hooks).
3. Run pre-commit hook manually on all files pre-commit run black -a (look at --from-ref and --to-ref options if you want to just format the files you modified)
4. Merge master into your branch