Apply gersemi to code base

[knoepfel]

Pursuant to #169, this PR applies gersemi to the phlex code base. This PR also changes the gersemi's default indentation from 4 spaces to 2, consistent with what was used for cmake-format.

[knoepfel]

Duplicates #239

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

❌ Your project status has failed because the head coverage (76.50%) is below the target coverage (80.00%). You can increase the head coverage or adjust the target coverage.

@@            Coverage Diff             @@
##             main     #238      +/-   ##
==========================================
- Coverage   76.61%   76.50%   -0.11%     
==========================================
  Files         124      124              
  Lines        2733     2733              
  Branches      475      475              
==========================================
- Hits         2094     2091       -3     
- Misses        446      447       +1     
- Partials      193      195       +2     

Flag	Coverage Δ
unittests	76.50% <ø> (-0.11%)	⬇️

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see 4 files with indirect coverage changes

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