ci: improve test workflow performance

[afuetterer]

This PR does two things. Please have a look at it and tell me what you think.

1. it speeds up the package and dependency installation by using uv instead of pip
2. it runs the pytest suite in parallel

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.00%. Comparing base (4735725) to head (77727c7).
Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #333   +/-   ##
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  Coverage   86.00%   86.00%           
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  Files          17       17           
  Lines        4209     4209           
  Branches      989      989           
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  Hits         3620     3620           
  Misses        430      430           
  Partials      159      159           

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[lkstrp]

uv ❤️

Looks great, thanks a lot as always @afuetterer
Would you mind adding the changes to PyPSA/powerplantmatching#182?

All the repos I'll update after a powerplantmatching release.

[afuetterer]

Sometimes there are a few hickups during the ci run, especially with the windows runners? It should take more than 2-3 minutes per test run.

[FabianHofmann]

looks great, we had a small printout of tested solvers in the log before, https://github.com/PyPSA/linopy/actions/runs/10074914889/job/27852237849#step:10:38

any chance to revive that again or have a logger info statement?