[llvm-branch-commits] [RISCV] Port MoveMergePass to NewPM (PR #235504)

[Aiden Grossman via llvm-branch-commits]

https://github.com/boomanaiden154 created https://github.com/llvm/llvm-project/pull/235504

Standard NewPM pass porting. Also note in the LegacyPM that this pass
preserves the CFG.