rename `Image3D` to `Model3D`

[pngwn]

@osanseviero mentioned:

Maybe it's a bit late and really it's a nit, but could help align with CV community, but I was wondering if Image3D should actually be called Geometry3D . I don't think someone would consider a point cloud or a mesh an image.

After a short discussion we felt that Model3D would be the best term as it is the most correct, despite this minor concern:

But it might confuse people unfamiliar to 3D CV that will think model=ML model

We have only just released this component so usage will be low and with 3.0 around the corner changing the name should be pretty safe.

[osanseviero]

Strong support for this, Model3D or Scene3D can be much better aligned to the CV community

[omerXfaruq]

I feel like naming Image3Dis better for a 3D Image, I don't get the feelings of a 3D Image from Model3D

[osanseviero]

Within the audience that would use this component, I think Model3D is clearer. Image implies 2D (or multichannel) data, while Model3D is a bit clearer about working with a 3D object.

See https://pytorch3d.org/ which uses load_obj for example, https://en.wikipedia.org/wiki/Wavefront_.obj_file which uses "3D geometry", https://en.wikipedia.org/wiki/GlTF which uses "three-dimensional scenes and models", or the recent Kubric https://github.com/google-research/kubric, which uses object as well. I don't think Image is very aligned with the community that would use the component.

[abidlabs]

Can we also use this opportunity to fix the bug that prevents cached Image3d examples from being loaded?

[abidlabs]

Renamed in components.py. Thanks @dawoodkhan82!