Enable FFT solver for MAC projections

[moprak-nrel]

Summary

Update the CMake files to enable FFT for MAC projections. Regtests and GPU testing incoming shortly.

Pull request type

Please check the type of change introduced:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

Checklist

The following is included:

• new unit-test(s)
• new regression test(s)
• documentation for new capability

This PR was tested by running:

• the unit tests
  • on GPU
  • on CPU
• the regression tests
  • on GPU
  • on CPU

Additional background

Issue Number:

[moprak-nrel]

Still in early stages for this PR. Needs regtests, and some guardrails for when the FFT solver should be enabled. Also need to add documentation for the input option to enable this feature.