EllipsoidShape: use const references in API

[scpeters]

🦟 Bug fix

Fixes API issue noted in #515 (comment)

Summary

Pass the Vector of Ellipsoid radii as a const reference to SetRadii and AttachEllipsoidShape. This is either an API or ABI break, so I've targeted main.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov]

Codecov Report

Merging #521 (efdb243) into main (2c93fdb) will not change coverage.
The diff coverage is n/a.

❗ Current head efdb243 differs from pull request most recent head 6e2f7f3. Consider uploading reports for the commit 6e2f7f3 to get more accurate results

@@           Coverage Diff           @@
##             main     #521   +/-   ##
=======================================
  Coverage   75.57%   75.57%           
=======================================
  Files         142      142           
  Lines        7193     7193           
=======================================
  Hits         5436     5436           
  Misses       1757     1757           

Impacted Files	Coverage Δ
bullet-featherstone/src/ShapeFeatures.cc	91.21% <ø> (ø)
dartsim/src/ShapeFeatures.cc	79.44% <ø> (ø)
include/gz/physics/EllipsoidShape.hh	100.00% <ø> (ø)
include/gz/physics/detail/EllipsoidShape.hh	100.00% <ø> (ø)
tpe/plugin/src/ShapeFeatures.cc	72.10% <ø> (ø)

[scpeters]

the macOS test failure is pre-existing on main

• https://build.osrfoundation.org/job/ignition_physics-ci-main-homebrew-amd64/75/testReport/junit/(root)/COMMON_TEST_simulation_features_bullet-featherstone/test_ran/

I'm going to merge