Fix Bullet ellipsoid rolling

[jslee02]

Summary

• fix Bullet ellipsoid rolling by using sphere shape for equal radii and a multi-sphere approximation otherwise
• fall back to the legacy mesh only if multi-sphere creation fails
• add a Bullet integration test that checks ellipsoid and sphere rolling on a ramp

Fixes #868

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• Add unit tests for new functionality
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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 61.72%. Comparing base (f891d7e) to head (20ca884).
⚠️ Report is 239 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2274      +/-   ##
==========================================
+ Coverage   61.70%   61.72%   +0.02%     
==========================================
  Files         360      360              
  Lines       32520    32537      +17     
  Branches     4271     4273       +2     
==========================================
+ Hits        20067    20084      +17     
  Misses      12453    12453              

Flag	Coverage Δ
unittests	61.72% <ø> (+0.02%)	⬆️

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see 1 file with indirect coverage changes

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[chatgpt-codex-connector]

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[jslee02]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Swish!

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