Tracking: `uv` transition

[dangotbanned]

Acting as a parent for the completed and outstanding work from #3577

Migrate active PRs

Mostly just merging to (21f5849).
Some change pyproject.toml and therefore need to sync uv.lock

• docs(example): Adds Confidence Interval Ellipses #3747 (f72da5a)
• feat(RFC): Adds altair.datasets #3631 (5975a8b)
• docs: Improved docs on Transforms #2655 (796a86e)
• feat(RFC): Adds agg, field utility classes #3505 (commits)
• feat: Extend .interactive() with tooltip and legend  #3394 (3319bab)

Needs issue

• uv lock --upgrade workflow (Add uv lock --upgrade CI workflow #3796)