[clang] [LifetimeSafety] Introduce buildOriginFlowChain for use-after-scope (PR #199345)

[Utkarsh Saxena via cfe-commits]

usx95 wrote:

As discussed over chat, I will merge this for now and we can add the test in a separate PR. This would unblock me from doing a couple of refactorings.

https://github.com/llvm/llvm-project/pull/199345