[chore][cmd/mdatagen] Enhance schema ID resolution for local references

[jkoronaAtCisco]

Description

This pull request provides fix for json schema generator: fixed a gap in schema ID resolution algorithm: local refs with relative paths (./...) were previously not resolved against a local-absolute origin schema ID — they are now correctly joined.

Link to tracking issue

Related to #14559

Testing

New test cases added to namespace_test.go

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 7 untouched benchmarks
⏩ 76 skipped benchmarks¹

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_{Comparing jkoronaAtCisco:fix_jsonschema_generator (38cf8e9) with main (ec18380)}

Footnotes

1. 76 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.39%. Comparing base (ec18380) to head (38cf8e9).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #14770      +/-   ##
==========================================
- Coverage   91.39%   91.39%   -0.01%     
==========================================
  Files         695      695              
  Lines       44400    44403       +3     
==========================================
  Hits        40581    40581              
- Misses       2686     2688       +2     
- Partials     1133     1134       +1     

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