FillPatcher for face-centered data

[BenWibking]

We have MHD in Quokka now. It would be very useful to be able to use FillPatcher for B-fields, but this is currently not supported:

amrex/Src/AmrCore/AMReX_FillPatcher.H

Line 58 in 65bf80d

* (5) This only works for cell-centered and nodal data.

For filling ghost zones, we don't need FaceDivFree. I think it's not possible to exactly preserve div B in coarse ghost regions with AMR subcycling anyway.