[llvm] [AMDGPU] Move SGPR Count Queries into TargetParser (PR #209848)

[Shilei Tian via llvm-commits]

shiltian wrote:

> I don't know how far you're able to take this, but I'm interested in moving SubtargetFeatures, defined in tablegen in the backend, into TargetParser. This bitfield in AMDGPUTargetParser.def is mirroring an arbitrary subset of those, with no formal link between them

The furthest needed would be something like what comgr is like at this moment, I think.

https://github.com/llvm/llvm-project/pull/209848