[clang] [llvm] [clang] Implement lifetime analysis for lifetime_capture_by(X) (PR #115921)

[Utkarsh Saxena via llvm-commits]

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usx95 wrote:

These were done in the non-analysis PR 
https://github.com/llvm/llvm-project/pull/115823

Checking whether `X` can actually capture has come up a couple of times and I will do this in a followup.

https://github.com/llvm/llvm-project/pull/115921