Use capture group to find Unity version to support new 6000 versions

[AndrewKahr]

Changes

• Support new Unity versioning scheme (https://forum.unity.com/threads/unity-6-new-naming-convention.1558592/)

Checklist

• Read the contribution guide and accept the
  code of conduct
• Docs (If new inputs or outputs have been added or changes to behavior that should be documented. Please make a PR
  in the documentation repo)
• Readme (updated or not needed)
• Tests (added, updated or not needed)

[github-actions]

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 36.97%. Comparing base (fc0a52b) to head (b8c45ef).

❗ Current head b8c45ef differs from pull request most recent head b2b7551. Consider uploading reports for the commit b2b7551 to get more accurate results

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #639      +/-   ##
==========================================
- Coverage   36.99%   36.97%   -0.03%     
==========================================
  Files          77       77              
  Lines        3122     3121       -1     
  Branches      609      645      +36     
==========================================
- Hits         1155     1154       -1     
+ Misses       1967     1824     -143     
- Partials        0      143     +143     

Files	Coverage Δ
src/model/unity-versioning.ts	100.00% <100.00%> (ø)

... and 37 files with indirect coverage changes