[llvm] [CodeGen] Add MachineRegisterClassInfo analysis pass (PR #120690)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Is any pass ever going to invalidate this analysis? If not, can we mark it as preserved in `MachineFunctionPass::getAnalysisUsage`?

The AMDGPU wwm alloc pass will need to 

https://github.com/llvm/llvm-project/pull/120690