refactor(yaml): cleanup `inspectNode()`

[timreichen]

• replaces duplicatesIndexes array with Set of objects
• reduces nesting and adds early returns

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.81%. Comparing base (81943c3) to head (221642e).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #5311 +/- ## ========================================== - Coverage 95.81% 95.81% -0.01% ========================================== Files 458 458 Lines 37883 37870 -13 Branches 5567 5566 -1 ========================================== - Hits 36298 36285 -13 Misses 1545 1545 Partials 40 40 ```

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