Replace Flake8 checks with Ruff (except for flake8-pyi)

[Avasam]

I got curious to see if we could replace the rest of Flake8 (but keeping flake8-pyi and with it flake8-noqa) with Ruff.
I've also been less selective about UP and RUF rules.

This is the result.
The bigger challenges and possible roadbump I'd say are astral-sh/ruff#3011 and plinss/flake8-noqa#22 / plinss/flake8-noqa#30

There's a couple things here that can be immediately useful that I'll split up into smaller PRs.

[Avasam]

warning: Invalid rule code provided to # ruff: noqa at stubs/six/six/moves/builtins.pyi:1: NQA102

docs.astral.sh/ruff/settings/#lint_external

NQA is already marked as external. I opened astral-sh/ruff#10202

[Avasam]

This will conflict with #11522 and some Ruff config changes don't make sense w/o the pre-commit changes, so we can't have this PR work standalone whilst avoiding conflicts. Keeping as draft for now for that reason.

[AlexWaygood]

Very nice! One comment suggestion, and one question:

[AlexWaygood]

LGTM!

[AlexWaygood]

If we did want to use extend-select rather than select in pyproject.toml, we could possibly do something like this:

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index dc4bc138b..9612c5417 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -20,12 +20,12 @@ repos:
         # Run this separately because we don't really want
         # to use --unsafe-fixes for all rules
         name: Remove unnecessary `sys.version_info` blocks
-        args: ["--exit-non-zero-on-fix", "--select=UP036", "--unsafe-fixes"]
+        args: ["--isolated", "--target-version=py38", "--exit-non-zero-on-fix", "--select=UP036", "--fix", "--unsafe-fixes"]
       - id: ruff
         # Very few rules are useful to run on our test cases;
         # we explicitly enumerate them here:
         name: Run ruff on the test cases
-        args: ["--exit-non-zero-on-fix", "--select=FA,I", "--no-force-exclude", "--unsafe-fixes"]
+        args: ["--isolated", "--target-version=py38", "--exit-non-zero-on-fix", "--select=FA,I", "--no-force-exclude", "--fix", "--unsafe-fixes"]
         files: '.*test_cases/.+\.py$'

But I personally find this PR's current solution cleaner!

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉