DRAFT: Highly experimental!!

Description

Fixes #5228

• Could some CI jobs be substantially accelerated using `uv pip` instead of `pip`? #5228

Creating Pyodide pull requests often requires several commits to get things working correctly and all tests passing. Unfortunately, there are numerous, long test runs on GitHub Actions and CircleCI so waiting for feedback can slow innovation. Pip installing numerous, large dependencies seems to be a substantial portion of the time required to run all these CI jobs.

Could some CI jobs be substantially accelerated using uv pip instead of pip?

https://docs.astral.sh/uv -- `10-100x faster than pip` sounds like a useful improvement to me.
https://github.com/astral-sh/uv/blob/main/BENCHMARKS.md

If there is interest in trying this and a maintainer can recommend one CI job to start with, I would like to create a proof-of-concept pull request to benchmark the performance improvement of using uv for that job.

Related to:

#5018 (comment)
#5004 (comment)

Let's start just with the instances of pip install in one file: .circleci/config.yml

When using uv, the virtual environment does not need to be activated. uv will find a virtual environment (named .venv) in the working directory or any parent directories. -- https://docs.astral.sh/uv/reference/cli/#uv-venv

@dhruvmanila Any advice on how to avoid repeated source .venv/bin/activate calls inside complex CircleCI jobs? https://docs.astral.sh/uv does not yet mention CircleCI.

Checklists

• Add a CHANGELOG entry
• Add / update tests
• Add new / update outdated documentation