[NewPM][AMDGPU] Make amdgpu-aa work with NewPM

An AMDGPUAA class already existed that was supposed to work with the new
PM, but it wasn't tested and was a bit broken.

Fix up the existing classes to have the right keys/parameters.
Wire up AMDGPUAA inside AMDGPUTargetMachine.

Add it to the list of alias analyses for the "default" AAManager since
in adjustPassManager() amdgpu-aa is added into the pipeline at the
beginning.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D93914