Update CI and simplify platform and version matrix

[marcelmbn]

• more recent gcc versions
• more recent GitHub Actions

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 43.15%. Comparing base (fcf7c14) to head (c5513f1).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #27   +/-   ##
=======================================
  Coverage   43.15%   43.15%           
=======================================
  Files          11       11           
  Lines        3119     3119           
  Branches      961      961           
=======================================
  Hits         1346     1346           
  Misses       1581     1581           
  Partials      192      192           

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