Drop Python 2.x support and fix CI

[topolarity]

This changes PyCall's minimum Python version to 3.3, since that is still many years out-of-life and allows us to remove most special cases for compatibility. Also adds macOS arm64 to CI.

Supersedes #1075.

Resolves #1099.

[topolarity]

I believe this is ready to go!

[topolarity]

Looks like setup-python does not understand architecture: default sadly

[topolarity]

@giordano I don't think the default change worked out, but I did switch to macos-15-intel

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.07%. Comparing base (2f600fb) to head (3197e31).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1098      +/-   ##
==========================================
+ Coverage   68.02%   69.07%   +1.04%     
==========================================
  Files          20       20              
  Lines        2036     1995      -41     
==========================================
- Hits         1385     1378       -7     
+ Misses        651      617      -34     

Flag	Coverage Δ
unittests	69.07% <100.00%> (+1.04%)	⬆️

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[abhro]

What are the "Expected — Waiting for status to be reported" checks?

[giordano]

Jobs which are marked as required in the settings, but didn't run because the the workflow changed. Either someone with enough power will have to bypass the jobs not running, or an admin needs to change the required jobs.