Update workflow runners, add clang-20

[Bronek]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.5%. Comparing base (5205895) to head (eb711b7).
Report is 2 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #158   +/-   ##
=====================================
  Coverage   99.5%   99.5%           
=====================================
  Files         19      19           
  Lines        827     827           
  Branches     121     121           
=====================================
  Hits         823     823           
  Misses         4       4           

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