[AMDGPU] Enable PreRARematerialize scheduling pass with multiple high RP regions

Enable the PreRARematerialize pass when there are multiple high RP scheduling
regions present. Require the occupancy in all high RP regions be improved
before finalizing sinking. If any high RP region did not improve in occupancy
then un-do all sinking and restore the state to before the pass.

Reviewed By: rampitec

Differential Revision: https://reviews.llvm.org/D122501