[llvm] [CodeGen][NewPM] Split `MachineDominatorTree` into a concrete analysis result (PR #94571)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

> We may need a machine dominator tree version of DomTreeUpdater to handle SplitCriticalEdge in some CodeGen passes.

I'm surprised this doesn't already exist 

https://github.com/llvm/llvm-project/pull/94571