feat: Add API for requesting a new mesh from the MeshManager

[azeey]

🎉 New feature

Summary

This allows allocating new common::Mesh objects within the gz-common shared library avoiding cross-shared library lifetime mismatch issues. Such issues currently cause a segfault in gz-physics COMMON_TEST_collisions_bullet-featherstone test, even though Jenkins doesn't report it (I'm working on a fix for that too).

Test it

Run UNIT_MeshManager_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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[caguero]

Looks good besides one minor comment.

My only other question is whether we should deprecate AddMesh() in favor of CreateMesh() or consider to add a comment in AddMesh() about the issue and the option to use CreateMesh().

[azeey]

I think deprecating AddMesh is a good idea. Done in db245f8. I will have a follow up on gz-sim to use CreateMesh instead.