Creates spectral ops test suite (#42157)
Summary:
In preparation for creating the new torch.fft namespace and NumPy-like fft functions, as well as supporting our goal of refactoring and reducing the size of test_torch.py, this PR creates a test suite for our spectral ops.
The existing spectral op tests from test_torch.py and test_cuda.py are moved to test_spectral_ops.py and updated to run under the device generic test framework.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/42157
Reviewed By: albanD
Differential Revision: D22811096
Pulled By: mruberry
fbshipit-source-id: e5c50f0016ea6bb8b093cd6df2dbcef6db9bb6b6
