ci: ignore JMH and test fixtures for coverage

[stuebingerb]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.96%. Comparing base (699a84a) to head (106f981).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #378      +/-   ##
==========================================
+ Coverage   74.72%   75.96%   +1.24%     
==========================================
  Files         162      156       -6     
  Lines        5151     5064      -87     
  Branches      906      897       -9     
==========================================
- Hits         3849     3847       -2     
+ Misses        961      876      -85     
  Partials      341      341              

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