Drop `mayavi` in favor of `vedo` or `pyvista`

[Sbozzolo]

mayavi, the Python package that we've used so far for 3D visualization, has been an endless source of pain (from a packaging point of view). Some of the problems come from VTK itself (e.g., they just added support to Python 3.10, one year after it was released), but others come from mayavi itself. In addition to this, mayavi doesn't seem actively developed and we do not have too much code that relies on it. For these reasons, I want to drop mayavi and use vedo or pyvista instead.

We don't need very sophisticated features. Both the packages seem to be heavily focused on meshes, which is not something that we strongly need (we only need them for horizons). We primarily need volumetric rendering and field lines.

3D visualization has not been my focus for a while, but kuibit has all the capabilities to enable cool animations. I am opening this issue to collect ideas and experiences. If anyone wants to help, I am happy to work with them to figure out the best solution.