[llvm] [DSE] Refactor DSE (PR #100956)

[Arthur Eubanks via llvm-commits]

aeubanks wrote:

also, the dependency cycle between Memory*Wrapper and DSEState is awkward, is it possible to keep the `eliminateDeadDefs()` implementations as part of DSEState?

https://github.com/llvm/llvm-project/pull/100956