Switch python toolchain to use ruff and uv

[rachitnigam]

ruff and uv are two new tools to make the formatting/linting and tool installation for python better. Let's switch from using the weird mix of flit, black, and flake8 to simply and consistently using ruff and uv (I know @sampsyo has already made this switch for Bril).

[EclecticGriffin]

If we want to do this migration in stages, the formatting side should be pretty simple. We can basically just run ruff format --check instead of the call to black. The linting is ruff check (though it seems there are a fair number of lints to fix).

Both can be accomplished via https://github.com/astral-sh/ruff-action.

[rachitnigam]

Let's do it!