[llvm] [NewPM][CodeGen] Add callback style codegen pass builder (PR #108690)

[via llvm-commits]

paperchalice wrote:

> I think I'm not understanding why the extension callback and the eraseIf are in the same PR, they seem like different things?

Moved this part to #116734.

https://github.com/llvm/llvm-project/pull/108690