Use uv for development environments instead of pixi

[mdekstrand]

This replaces Pixi with uv for the development environments to simplify them.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.91%. Comparing base (c75ec60) to head (d7acc2f).
Report is 22 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #700      +/-   ##
==========================================
+ Coverage   90.88%   90.91%   +0.03%     
==========================================
  Files         134      134              
  Lines        9295     9295              
==========================================
+ Hits         8448     8451       +3     
+ Misses        847      844       -3     

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