Add per-op MPS gradient tests and update skips (#84242)
Follow up:
- ~Remove non-float dtypes from allow-list for gradients~
- ~Map dtypes to short-hand so there aren't so many lines, i.e. float16 should be f16.~
- ~There were a lot of linting issues that flake8 wouldn't format for me, so I reformatted with black. This makes the diff a little trickier to parse.~
Observations:
- there are entries in the allow-list that weren't there before
- some forward that we previously passing now fail with requires_grad=True
- Because the allow list does not know about variants, a special skip was added for that in the block list
Pull Request resolved: https://github.com/pytorch/pytorch/pull/84242
Approved by: https://github.com/kulinseth, https://github.com/malfet
