Add pocketfft as submodule (#62841)
Summary:
Using https://github.com/mreineck/pocketfft
Also delete explicit installation of pocketfft during the build as it will be available via submodule
Limit PocketFFT support to cmake-3.10 or newer, as `set_source_files_properties` does not seem to work as expected with cmake-3.5
Partially addresses https://github.com/pytorch/pytorch/issues/62821
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62841
Reviewed By: seemethere
Differential Revision: D30140441
Pulled By: malfet
fbshipit-source-id: d1a1cf1b43375321f5ec5b3d0b538f58082f7825
