refactor(yaml): cleanup utility functions

[timreichen]

Changes
This PR removes makes isPlainSafeFirst() call isPlainSafe() and removes double checks.
It also removes unhelpful comments and adds jsdoc comments to the functions.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.33%. Comparing base (f86e911) to head (c9b213b).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5886      +/-   ##
==========================================
- Coverage   96.34%   96.33%   -0.01%     
==========================================
  Files         479      479              
  Lines       38674    38656      -18     
  Branches     5631     5623       -8     
==========================================
- Hits        37260    37241      -19     
- Misses       1370     1371       +1     
  Partials       44       44              

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[iuioiua]

Thank you