High-order coordinates via interpolated DMPlex

[pbrubeck]

• PETSc now owns the high-order coordinate PetscFE, section, and vector.
• Coordinates are inserted through oriented DMPlex closures in compiled Cython.
• Firedrake imports the distributed coordinate field into a normal coordinate Function.
• Removed physical point matching, find_permutation, netgen_distribute, sfBC_orig, and dynamic netgen_mesh/netgen_flags attributes.
• Adaptive refinement and geometric multigrid preserve high-order geometry in serial and MPI.
• Initial Netgen processing can be rank-zero-only; geometry is replicated lazily when distributed refinement needs local evaluation.

[UZerbinati]

I'm happy with this, let me know when I need to merge and if a release is needed :)

[pbrubeck]

I'm happy with this, let me know when I need to merge and if a release is needed :)

The Firedrake counterpart should probably go into release, as this will fix the problems with the self-intersecting cells that we were getting on high-order meshes