[llvm] [NewPM][CodeGen][WIP] Add callback style CodeGen pass pipeline builder (PR #104725)

[Arthur Eubanks via llvm-commits]

https://github.com/aeubanks commented:

we should add the corresponding places in the pipeline that invoke the callbacks in this PR as well

this conceptually makes sense

https://github.com/llvm/llvm-project/pull/104725