Sunset MeshProperties, introduce TriangleIndices and friends

[teh-cmc]

MeshProperties was a hack that was required because of the old join semantics.
We can now make Mesh3D.triangle_indices what we always intended: a Vec<UVec3>.

(This won't work in the web viewer generated by this PR since it breaks the Mesh3D ABI.)

• Fixes Get rid of awkward MeshProperties #5402

Migrations

C++

  rerun::Mesh3D(positions)
-     .with_mesh_properties(rerun::components::MeshProperties::from_triangle_indices({{2, 1, 0}}))
+     .with_triangle_indices({{2, 1, 0}})

Python

  rr.Mesh3D(
      vertex_positions=…,
-     indices=[2, 1, 0],
+     triangle_indices=[2, 1, 0],
  ),

Rust

  rerun::Mesh3D::new(positions)
-     .with_mesh_properties(rerun::MeshProperties::from_triangle_indices([[2, 1, 0]]))
+     .with_triangle_indices([[2, 1, 0]])

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using examples from latest main build: rerun.io/viewer
  • Using full set of examples from nightly build: rerun.io/viewer
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG
• If applicable, add a new check to the release checklist!

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[github-actions]

Deployed docs

Commit	Link
62848df	https://landing-68yhs41b3-rerun.vercel.app/docs

[teh-cmc]

I have absolutely no idea why this was the only one with nullability baked in oO.

Probably an old hack if I had to guess...

[jleibs]

This still breaks join semantics.

You've just made it so that breaking join semantics is now allowed and the knowledge of how to join is implicitly deferred to the visualizer.

I still think we should consider introducing a "non-joinable" attribute as an annotation for components where the conventional join is known not to work to help us out with things like instance-selection.

[teh-cmc]

@rerun-bot full-check

[github-actions]

Started a full build: https://github.com/rerun-io/rerun/actions/runs/8893612099