[clang] [clang] Introduce [[clang::lifetime_capture_by(X)]] (PR #111499)

[Utkarsh Saxena via cfe-commits]

usx95 wrote:

> I did not get to the end of this PR yet, but I was wondering if it would make sense to split it up. One PR could add the attribute with the semantic analysis (e.g., warnings for ill-formed arguments). The second PR could introduce the lifetime analysis part. WDYT?

Makes sense. I will do this now.

https://github.com/llvm/llvm-project/pull/111499