Feature/stft no window warn (#110695)
Fixes #88919
@mruberry @peterbell10
This PR adds a warning to the .cpp STFT and ISTFT functions if a window is not provided.
It also describes the warning in the documentation on `functional.py`.
Finally, it adds unit tests to check if the warning is being produced.
I have audited for internal calls of `stft` and `istft` on Pytorch and haven't found any.
Thank you for the opportunity to contribute!
Eric
Pull Request resolved: https://github.com/pytorch/pytorch/pull/110695
Approved by: https://github.com/ezyang
