[AMDGPU] gfx11 subtarget features & early tests

Tablegen definitions for subtarget features and cpp predicate functions to
access the features.
New Sub-TargetProcessors and common latencies.
Simple changes to MIR codegen tests which pass on gfx11 because they have the
same output as previous subtargets or operate on pseudo instructions which
are reused from previous subtargets.

Contributors:
Jay Foad <jay.foad@amd.com>
Petar Avramovic <Petar.Avramovic@amd.com>

Patch 4/N for upstreaming of AMDGPU gfx11 architecture

Depends on D124538

Reviewed By: Petar.Avramovic, foad

Differential Revision: https://reviews.llvm.org/D125261