[llvm] Reapply "[coro][CoroSplit] Use `llvm.lifetime.end` to compute putting objects on the frame vs the stack (#90265) (PR #91372)

[Nikita Popov via llvm-commits]

nikic wrote:

I was curious if just the SmallPtrSet change would be enough for the original implementation, but apparently not: https://llvm-compile-time-tracker.com/index.php?branch=nikic/perf/reachable It is a significant improvement, but not enough.

https://github.com/llvm/llvm-project/pull/91372