[llvm] [MemCpyOpt] fix incorrect handling of lifetime markers (PR #143782)

[Nikita Popov via llvm-commits]

https://github.com/nikic approved this pull request.

LGTM with the additional comments you added removed. I've finally gotten around to removing the size argument from these intrinsics (https://github.com/llvm/llvm-project/pull/150248), so this is now just landing part of that early.

https://github.com/llvm/llvm-project/pull/143782