Add generic device support to dft domain through portFFT

[s-Nick]

Description

This PR is the continuation of PR #566 and it is based on it.
It adds generic devices support by enabling portFFT and generic device the same way it is done for portBLAS.

Checklist

All Submissions

• Do all unit tests pass locally? Attach a log.
  • I don't have a non Intel/NVIDIA/AMD device to test with. Tests are successful when forcing Intel devices to go through generic_device path.

Following logs show that all domains still work properly:
portfft_log.txt
arc_blas_log.txt
cufft_log.txt
arc_lapack_log.txt
arc_rng_log.txt

• Have you formatted the code using clang-format?

New features

• Have you provided motivation for adding a new feature?
  Same reason added to Add generic device and initial support in portBLAS #566

• Have you added relevant tests?
  Generic device doesn't require new tests

[Rbiessy]

LGTM

[lhuot]

LGTM, thanks!