mujoco: Support RemoveModelFromWorld feature

[iche033]

🎉 New feature

Addresses #299
Depends on:

• mujoco: Initial implementation #811
• mujoco: Add support for GetContactsFromLastStep feature #889

Summary

Added the RemoveModelFromWorld feature for mujoco plugin.

• Implemented various RemoveModel* functions
• Fixed a bug in SDFFeatures that calls GetNextEntity twice when constructing a model
• Nested models are not supported yet.

Test it

ctest -R UNIT_mujoco_SDFFeatures_TEST

Checklist

• Signed all commits for DCO
• Added a screen capture or video to the PR description that demonstrates the feature
• Added tests
• Added example and/or tutorial
• 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)
• Updated Bazel files (if adding new files). Created an issue otherwise.
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Generated-by: Gemini 3

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