[clang] [LifetimeSafety] Implement dataflow analysis for loan propagation (PR #148065)

[Utkarsh Saxena via cfe-commits]

usx95 wrote:

### Merge activity

* **Jul 14, 6:16 PM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/148065).


https://github.com/llvm/llvm-project/pull/148065