Deprecate MeshFromRefinements

[RemDelaporteMathurin]

I think it is time to deprecate MeshFromRefinements.

https://github.com/festim-dev/FESTIM/blob/main/festim/meshing/mesh_from_refinements.py

It is a very old class that have been replaced by MeshFromVertices in pretty much all demos and examples.

We should:

• Remove MeshFromRefinements
• Remove the tests
• Remove the documentation

I don't think we need to worry about backwards compatibility. I don't know a single user who uses this class.

If for some reason someone really needs it, please let us know here so that we can assist you.