Adds Device Generic Precision Tests to test_torch.py (#26762)
Summary:
- Lets device generic classes be instantiated for all available device types EXCEPT those specified
- Creates TestDevicePrecision in test_torch.py, letting devices compare their results to the CPU's
- Moves 4 functions from test_cuda.py to TestDevicePrecision
- polygamma and digamma functions were cleaned up
The polygamma and digamma tests always ran with double tensors and will fail when using float tensors, despite former comments and code to the contrary. Notes were added to each function.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26762
Differential Revision: D17677859
Pulled By: mruberry
fbshipit-source-id: 7cbe7d05ee0bc9b622c9127be36ced02f9c4506a
