Add Python 3.12 into github testing CI

[yarikoptic]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.55%. Comparing base (32c8b14) to head (9d481a6).
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #799      +/-   ##
==========================================
+ Coverage   82.46%   82.55%   +0.09%     
==========================================
  Files          42       42              
  Lines        4323     4323              
==========================================
+ Hits         3565     3569       +4     
+ Misses        758      754       -4     

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[yarikoptic]

3.13 -- is something scary

  import traits.ctraits
E   ImportError: /opt/hostedtoolcache/Python/3.13.0/x64/lib/python3.13/site-packages/traits/ctraits.cpython-313-x86_64-linux-gnu.so: undefined symbol: Py_TRASHCAN_SAFE_BEGIN

let's tame the horses a little.