[CUDA] Add FFT support

[lucasnewman]

Proposed changes

This adds CUDA parity with Metal for FFT ops, as requested in #2561

The implementation uses cufft and is inspired by nvmath-python which is referenced in that issue. I tried to make this as minimal as possible, and I verified all the tests for both python and cpp pass as expected, including the disabled-in-CI exhaustive one, test_fft_exhaustive.

I only had access to an H200 with CUDA 12.4 for testing -- if there's an easy way to test on other hardware, let me know and I can try it.

Checklist

Put an x in the boxes that apply.

• I have read the CONTRIBUTING document
• I have run pre-commit run --all-files to format my code / installed pre-commit prior to committing changes
• I have added tests that prove my fix is effective or that my feature works
• I have updated the necessary documentation (if needed)

[zcbenz]

This is overall very nice, thanks a lot writing this!

[zcbenz]

Can you enable the FFT tests in python/tests/cuda_skip.py and .github/actions/test-linux/action.yml?

[lucasnewman]

@zcbenz Thank you for the review! I think I've addressed everything you mentioned, and tests are passing for me on my CUDA setup. Let me know if there's anything else needed.

[zcbenz]

Just a few more nitpickings, and this looks good to me!