[llvm] [AMDGPU] Move LDS utilities from amdgpu-lower-module-lds pass to AMDGPUMemoryUtils (PR #88002)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Why is AMDGPUMemoryUtils in the Utils directory? I thought that was only for stuff shared between CodeGen and the assembler/disassembler?

That's the main reason for the split. It's OK to refer to IR there though, so this isn't problematic as-is. However, it is somewhat out of place 

https://github.com/llvm/llvm-project/pull/88002