Bunch of Fixes

[brendancol]

The following PR includes a bunch of fixes that I need to get CI/CD working again.

The most technically unstable is an update to experimental/polygonize.py which now has a custom implementation of generated_jit, but should in the future use nb.extends.overload style...

I also:

• got codecov working again
• added Python 3.12 support to CI/CD
• dropped 3.8 / 3.9 support from CI/CD

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.04%. Comparing base (27ab0c8) to head (a83bf9b).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #796      +/-   ##
==========================================
+ Coverage   79.94%   80.04%   +0.10%     
==========================================
  Files          19       19              
  Lines        4178     4179       +1     
==========================================
+ Hits         3340     3345       +5     
+ Misses        838      834       -4     

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[tcmetzger]

Thanks!