[llvm] [AMDGPU] Introduce "amdgpu-sw-lower-lds" pass to lower LDS accesses. (PR #87265)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> We could consider splitting this pass, first lowering of LDS to global memory and then instrumenting newly lowered memory operations as future work.

This would be much better and we should do this. That was what I wanted at the beginning, and why I wanted this renamed to lower SW LDS. As it is, the name is misleading because it's not software LDS lowering when it's mixing in all the sanitizer handling 

https://github.com/llvm/llvm-project/pull/87265