Move requirements to dev dependency group and consistent dep version in tests

[Avasam]

Must wait for the next release of pip that will support PEP 735 thanks to pypa/pip#13065

• The Ruff version is now obtained automatically from the listed requirements, both in CI and locally.
• "hygiene" and "tests" still have different sets of dependencies
• Running pip install --group dev or uv sync will install all dev-dependencies

[Avasam]

Pip 25.1 is out with https://ichard26.github.io/blog/2025/04/whats-new-in-pip-25.1/#dependency-groups-pep-735 !

[debonte]

This isn't a new issue, but I'm curious why we're testing against matplotlib >=3.8 since those are the versions for which matplotlib ships their own stubs. 3.8.0 shipped back in September 2023. I wonder when we'll be comfortable removing our matplotlib stubs.

[Avasam]

skimage, sklearn and sympy all reference matplotlib !
Here it's considered "a typed library external to "python-type-stubs".
You want to test against matplotlib >=3.8 specifically because it's the version that provides their own types.

So once matplotlib stubs are removed from this repo, this line should stay.