feat: add getClusterOptions getter to GeoJSONSource

[lazerg]

Fixes #7788

Adds a getClusterOptions getter to GeoJSONSource that returns the source's current cluster configuration (cluster, clusterMaxZoom and clusterRadius), mirroring the options accepted by setClusterOptions. This lets callers check whether a source is clustered and read its clusterMaxZoom through the public API instead of reaching into worker internals.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.36%. Comparing base (02e7b0f) to head (9003802).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7948      +/-   ##
==========================================
- Coverage   93.38%   93.36%   -0.02%     
==========================================
  Files         288      288              
  Lines       24441    24446       +5     
  Branches     6461     6461              
==========================================
+ Hits        22824    22825       +1     
- Misses       1617     1621       +4     

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[CommanderStorm]

makes sense to me and LGTM

[HarelM]

Added a small comment on the test, once fixed this can be merged.