[llvm] [CodeGen] Replace CodeGenPassBuilder CRTP with virtual hooks (PR #216468)

[via llvm-commits]

paperchalice wrote:

In general I think we should discuss this in [[RFC] Codegen new pass manager pipeline construction design](https://discourse.llvm.org/t/rfc-codegen-new-pass-manager-pipeline-construction-design/84659)..
The only benefit from CRTP is polymorphic return type, i.e. user can return a module pass manager when builder expects a function pass manager, this feature is used in one of my pass builder prototypes.

https://github.com/llvm/llvm-project/pull/216468