test(yaml): test handling of boolean values

[kt3k]

part of #3713

This PR adds test cases to check parsing and serialization of booleans.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.49%. Comparing base (0629b71) to head (07fc3e5).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5251      +/-   ##
==========================================
+ Coverage   95.47%   95.49%   +0.02%     
==========================================
  Files         461      461              
  Lines       38002    38002              
  Branches     5535     5537       +2     
==========================================
+ Hits        36281    36291      +10     
+ Misses       1679     1669      -10     
  Partials       42       42              

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