refactor(yaml): add resolveTag() method

[timreichen]

This PR moves bloat from composeNode() into a separate resolveTag() method.
That code is also rewritten to be more readable.

[codecov]

Codecov Report

❌ Patch coverage is 92.10526% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.14%. Comparing base (6ee055f) to head (98fdb06).

Files with missing lines	Patch %	Lines
yaml/_loader_state.ts	92.10%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6904      +/-   ##
==========================================
- Coverage   94.14%   94.14%   -0.01%     
==========================================
  Files         582      582              
  Lines       42750    42749       -1     
  Branches     6807     6810       +3     
==========================================
- Hits        40245    40244       -1     
  Misses       2455     2455              
  Partials       50       50              

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