Replace flake8, bugbear, isort, and pyupgrade with ruff

[cclauss]

Fixes: #569

Ruff supports over 500 lint rules and can be used to replace Flake8 (plus dozens of plugins), isort, pydocstyle, yesqa, eradicate, pyupgrade, and autoflake, all while executing (in Rust) tens or hundreds of times faster than any individual tool.

The ruff Action uses minimal steps to run in ~5 seconds, rapidly providing intuitive GitHub Annotations to contributors.

Running the complete test matrix on GitHub Actions takes a lot of time and CPU. Given that the ruff linting job is so fast (~5 seconds) let's ensure that linting passes before the complete test matrix is run. This will cost a few seconds on each run but could save a lot of time and contention for PRs that should be cleaned up before they are fully tested.

https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idneeds

[sirosen]

I've been looking for a project to try out ruff, so putting it on nose2 would be interesting to me.

I want to give particular thanks for being diligent about ignoring things which could have changed semantics, especially on old pythons. It make reviewing this much easier!

There's the possibility of moving nose2's packaging configuration into pyproject.toml in the future to consider too.

Overall, a big 👍 for this. I look forward to seeing how it works out (and it can always be changed back in the future if necessary). Thanks!