Use tox-uv

[AdrianSosic]

Speedup our environment creation by using uv instead of pip via tox-uv.

The following times were obtained on my local machine by creating environments via tox --devenv toxenv -e audit-py39 (since audit installs all dev dependencies):

• tox: 64s
• tox-uv (no cache): 29s
• tox-uv (cached): 4s

[AdrianSosic]

@Scienfitz @AVHopp
Next to the local speedups, we do also get very decent speedups in the CI, see screenshots below. However, as you can see, one of the tests failed because of a timeout that can occur in CI with large dependencies such as torch. There is already an open issue (astral-sh/uv#1921).

What do we do? Manually adjust or (my preference:) just keep the PR up until they fixed the issue (which probably happens very soon) and only merge once our pipeline is stable with the default settings?

With tox:

With tox-uv: