[clang] [LifetimeSafety] Trace assignment history for use-after-scope errors (PR #188467)

[Yuan Suo via cfe-commits]

suoyuan666 wrote:

> > Hi, I’ve moved the assignment backtracking logic from `LifetimeChecker` into a dedicated file and refactored the diagnostic handling to align with the format you suggested.
> 
> I do not see the changes yet.

Sorry for the confusion; I meant that I had already completed those changes locally.
That makes sense now. I'll apply this assignment tracing logic to other diagnostics, run the local tests, and push the updates soon.

https://github.com/llvm/llvm-project/pull/188467