[AMDGPU] gfx11 Generate VOPD Instructions

We form VOPD  instructions in the GCNCreateVOPD pass by combining
back-to-back component instructions. There are strict register
constraints for creating a legal VOPD, namely that the matching operands
(e.g. src0x and src0y, src1x and src1y) must be in different register
banks. We add a PostRA scheduler
mutation to put possible VOPD components back-to-back.

Depends on D128442, D128270

Reviewed By: #amdgpu, rampitec

Differential Revision: https://reviews.llvm.org/D128656