What this MR does / why does DuMux need it:
- Adds two new interface to the box fv element geometry
geometry(scvf)that produce a geometry on-the-fly. This obviates the need for storing corners in the sub entities themselves.
- Deprecates box
- Adds a deprecation helper to get rid of deprecation warnings (but deprecation warning are not all fixed in this MR)
- Extends the interface of extrusion, necessary to have a more relaxed geometry interface
Follow-up from !3199 (merged).
Addresses #1173 for box
use new center from !3230 (merged)
Notes to reviewer: The changes lead to quite a lot of deprecation warnings which need to be fixed before the release. But I propose to do this in another cleanup MR. These changes will allow for a box scv/scvf implementation after the release which significantly reduces memory overhead when caching is enabled.