ci: switch flake8 by ruff

[andreaskoepf]

This PR supersedes #1159 (cloned OA repo was archived by original PR author).
Original text by Borda:

Ruff aims to be orders of magnitude faster than alternative tools while integrating more functionality behind a single, common interface.
Ruff can be used to replace Flake8 (plus dozens of plugins), isort, pydocstyle, yesqa, eradicate, pyupgrade, and autoflake, all while executing tens or hundreds of times faster than any individual tool.

Also, I would suggest installing pre-commit bot, which helps to fix code within each PR so, lowering developer overhead... see: https://pre-commit.ci/

[Borda]

cloned OA repo was archived by original PR author

I would unarchive if you would say that we may continue and eventually land the original PR :)

[andreaskoepf]

@Borda … your commits are in the new PR, I just merged main to ensure that pre-commit is passing with the latest source revision… which it is. Thanks again.

[yk]

lgtm, thank you