Tensor Product Additions

[alexfikl]

Implements a couple of small things for tensor products:

• Differentiation using Add gradient for tensor product basis modepy#13 (may need some version bumps?)
• Some version of face_vertex_indices that seems to allow building up the facial adjacency
• Expanded the check in _test_node_vertex_consistency
• Expanded some tests to check this stuff
• (inducer in Implement tensor product face restrictions alexfikl/meshmode#1) Update make_face_restriction.
• Unloaded all "reference element" details to modepy (needs Implement the face mass matrices for tensor products modepy#16).

Some remaining things to do:

• Refinement doesn't support tensor product elements.
  • WIP at Tensor product refinement alexfikl/meshmode#3
• Use Implement the face mass matrices for tensor products modepy#16 shapes and function spaces in more places.
• Test grudge with new versions of meshmode and modepy.
  • See CI: Run using modern modepy grudge#35
• Test pytential with new versions of meshmode and modepy.
  • See CI: Run using modern modepy pytential#44

[alexfikl]

By the way, I wasn't planning on updating make_face_restriction as part of this PR. It's quite a large chunk of code I don't understand..

[inducer]

Thanks for working on this!

By the way, I wasn't planning on updating make_face_restriction as part of this PR. It's quite a large chunk of code I don't understand..

See alexfikl#1 for "how hard could it possibly be". :)

[alexfikl]

Implemented mesh refinement for tensor product too. It turned out to be a bit big, so it's at alexfikl#3.

[inducer]

CI fails should get fixed by #96.

[inducer]

Thanks for working on this. This is 99.99% ready to go in my view. One concern, the rest of my comments are pretty superficial.

[alexfikl]

Re-runing inducer/grudge#35 and inducer/pytential#44 with latest changes.

[inducer]

Thanks! Made a small tweak (0c10f6b). Ready to go from my end, I'll merge after CI passes.