Not sure how these got missed when moving other things to `uv`, but this
should clean them up.
The bump to Python 3.12 is so that we can use `@override` with the
simple import from `typing`. This is needed by the newest versions of
`ty` to do type checking. Added the relevant `@override` annotations.
Assisted-by: Antigravity with Gemini
This removes the need to install any specific version of Python or
figure out how to configure it by instead asking users to install `uv`
and letting it manage Python. Among other advantages, `uv` is designed
to be fast enough to embed directly into our scripts.
We were already using this in `bench_runner.py` so that the script could
import non standard library dependencies. Moving to it for the rest of
our Python unifies the approach and will also enable dependencies
whenever needed.
I've left `github_tools` alone as it has special handling with its own
Bazel setup.
I've updated the contributing tools to explain the approach here.
Chandler Carruth
Jon Ross-Perkins