torch.fft: Two dimensional FFT functions (#45164)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45164
This PR implements `fft2`, `ifft2`, `rfft2` and `irfft2`. These are the last functions required for `torch.fft` to match `numpy.fft`. If you look at either NumPy or SciPy you'll see that the 2-dimensional variants are identical to `*fftn` in every way, except for the default value of `axes`. In fact you can even use `fft2` to do general n-dimensional transforms.
Test Plan: Imported from OSS
Reviewed By: ngimel
Differential Revision: D24363639
Pulled By: mruberry
fbshipit-source-id: 95191b51a0f0b8e8e301b2c20672ed4304d02a57
