Support ply format in gr.Model3D

[hysts]

• I have searched to see if a similar issue already exists.

I think .ply is a widely used format for 3D models and it would be nice if it was possible to directly visualize .ply files in gr.Model3D without the need to convert the format using other libraries like trimesh.

[hannahblair]

Looks like babylonjs doesn't support .ply files out of the box 😬 This could be a tricky one to handle.

[abidlabs]

We just added .ply support in #7406 (they are rendered as Gaussian splats) so I'll go ahead and close this issue (as based on internal discussion, it seems that the Gaussian splat use case is by far the more common one).