Expose Mesh::convex_decompose to scripts

[Ryan-000]

Describe the project you are working on

Im working on a large 3d game and I need to generate "Multiple Convex" Shape3D's from code for mass importing.

Describe the problem or limitation you are having in your project

Currently, the only way to do it is with MeshInstance3D::create_multiple_convex_collisions, but its very hacky to only get the Shape3D's since you need to instantiate a MeshInstance3D, then need to find the static body child, iteratate though its children of type CollsionShape3D and get the shapes that way, then you need to delete those nodes.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

You get to directly call Mesh::convex_decompose instead of hacking around it.

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

See godotengine/godot#102068

If this enhancement will not be used often, can it be worked around with a few lines of script?

N/A

Is there a reason why this should be core and not an add-on in the asset library?

N/A