Enable dt estimate for quads/hexes, extend tests for it

[inducer]

cc @MTCam

• Needs Fix support for zero-dimensional tensor product discretizations modepy#81
• Needs Remove TensorProductElementGroupBase.bases_1d meshmode#409
• Needs Avoid de/allocations for zero-sized temporaries loopy#840

[inducer]

Well... for some very innocuous-looking changes, this has some very exciting-looking failures. 😬

[MTCam]

Well... for some very innocuous-looking changes, this has some very exciting-looking failures. 😬

I forgot about these. At some point I had worked out a plan for how to fix these tests, but now have turned away too long to remember. I'll have another look.

[inducer]

Should check for supported element types instead.

[inducer]

@MTCam Now all the remaining failures are numerical in nature, illustrating (I think) that this does not find a valid time step estimate for tensor product elements even for wave.

[MTCam]

@MTCam Now all the remaining failures are numerical in nature, illustrating (I think) that this does not find a valid time step estimate for tensor product elements even for wave.

If we adjust the sketchy fudge factor in the wave operator's rk4 estimate to 0.23 for TPE. I think it passes. That fudge factor is dependent on element type.

I think I also added a skip for the dim=1 tests for TPEs as there is no 1D TPE.