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

[Arthur Eubanks via llvm-commits]

aeubanks wrote:

sorry, I meant that we should keep Memory*Wrapper as simple structs that just hold some data without any complex methods like `eliminateDeadDefs`, and then DSEState contains all the real logic, using Memory*Wrapper wherever necessary. not to move Memory*Wrapper under DSEState. Memory*Wrapper should probably be outside DSEState like before

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