Use ruff instead of flake8 + isort

[akx]

This may have dropped some of the lint rules that were implicitly enabled by hacking being installed, as well as E203 and W503; if that's a problem, I can take a closer look and see what the ruff equivalents are.

warning: Unsupported prefix code: E203
warning: Unsupported prefix code: W503
warning: Unsupported prefix code: H101
warning: Unsupported prefix code: H301
warning: Unsupported prefix code: H306
warning: Unsupported prefix code: H404
warning: Unsupported prefix code: H405

[ajmyyra]

Thank you for the PR! Linting by hacking isn't that relevant and we should replace them regardless, so losing them is fine. E203 would seem to be supported. W503 on the other hand is not supported, but I don't consider that a blocker as it's a non-violation and we're fixing a long-standing issue here. Could you rebase the branch so we can get it merged? Thanks again!

[akx]

@ajmyyra Ah yeah, E203 is a "nursery rule", so it's not activated by default. Since this repo is formatted by black, it's not really relevant anyway. :)

Rebasin'!