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

[via llvm-commits]

paperchalice wrote:

> @paperchalice are you planning to port Greedy allocator? If you haven't started, let us know, we're planning for it.

Currently my plan is to ensure that minimum codegen pipeline (incomplete O0 pipeline) can work and refactoring the pass builder (this pr), so I haven't touched greedy allocator part. Thanks for planning to port greedy allocator part!

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