Introducing tox-uv

[emdneto]

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uv makes pip install faster. It works like this: uv pip install and we can have tests running faster locally and in CI. The tool is from the creators of ruff.

The main improvement I see here is the Dependency caching and fast resolution of packages during pip install. We can benefit from this for local development to avoid slow tests, mainly the git clones in contrib tests.

This PR also introduces the usage of tox-uv which is a tox plugin that supports venv runner with uv.

At this first moment, I'm proposing an opt-in usage, so you need to pass an environment variable to make use of the UV feature.