optmap: remove functions for standalone optmap-evt files

[ManuelHu]

reading those files has not been possible, so also remove the last test for it and the corresponding code.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.94%. Comparing base (d31e919) to head (3cdbf10).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #153      +/-   ##
==========================================
- Coverage   70.04%   69.94%   -0.10%     
==========================================
  Files          33       33              
  Lines        2597     2582      -15     
==========================================
- Hits         1819     1806      -13     
+ Misses        778      776       -2     

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