[llvm] [AMDGPU] Enable architected SGPRs for GFX12 (PR #79160)

[Christudasan Devadasan via llvm-commits]

cdevadas wrote:

This patch LGTM. But it needs a rebase when https://github.com/llvm/llvm-project/pull/79120 is merged.
The test llvm/test/CodeGen/AMDGPU/lower-work-group-id-intrinsics.ll is renamed and a couple of similar tests might require changes.

https://github.com/llvm/llvm-project/pull/79160