[llvm] Reland "CodeGen][NewPM] Port MachineScheduler to NPM. (#125703)" (PR #126684)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

lgtm with a fixme to remove the extra forward declares and impls when RegisterClassInfo is queryable as an analysis 

https://github.com/llvm/llvm-project/pull/126684