[clang] [LifetimeSafety] Run analysis in post-order of CallGraph for better annotation propagation (PR #174178)

[Utkarsh Saxena via cfe-commits]

https://github.com/usx95 commented:

Very excited to see this working. This seems to be a great direction both for inference and template functions (as instantiations are deferred to end of TU) specially `std::make_unqiue` https://github.com/llvm/llvm-project/issues/163602.

Overall looks good. Couple of nits and some suggestions to for `CallGraph` creation.

Once this PR is in good shape, I would try to benchmark this to see compile-time hit using llvm-compile-time-tracker. We should quickly be able to get rid of the new frontend option and do analysis at end of TU by default if all goes fine.

https://github.com/llvm/llvm-project/pull/174178