rfc: speeding up with the oxidized `python` set

[HaoZeke]

For speed, i.e:

• ruff over black and blackendoc (e.g. Using ruff to format code examples in docstrings astral-sh/ruff#7146)
• uv over virtualenv (for the environments in nox not managed by micromamba/conda)
  • the nox cookbook has some nice uv driven examples including lockfile stuff (e.g. PEP 751) and there's some nice stuff here too

uv has provided speed benefits on metatensor/metatrain#787 and metatensor/metatensor#997 (will add it to metatomic soon too).

[pfebrer]

I personally don't feel that speed is an issue in the atomistic cookbook, but feel free to submit a PR