Modularize Vertical Diffusion Solver Step

### Issue Type

Code Clean-up, Infrastructure Update, Externals Update

### Issue Description

The current implementation of the vertical diffusion solver exposes the LU-decomposition methods/structures and setup directly to user. Minimizing exposed interfaces enables us to make the solver more portable and possible to export it to `atmospheric_physics`.

Propose wrapping the solve step in an interface that will allow interchangeability with different implantations without breaking user code and the implementation can be refactored into `atmospheric_physics`.

### Will this change answers?

No

### Will you be implementing this yourself?

Yes