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

[Alan Zhao via llvm-commits]

alanzhao1 wrote:

> > @alanzhao1 This still causes a regression, but it's possible to avoid it by removing the StopBBReachable set: [bfc261b](https://github.com/llvm/llvm-project/commit/bfc261b1c061b952992957e8892ce851afd6f84f) We don't really need this set, it's okay to set DT to nullptr if any of the stop BBs is not reachable.
> 
> This comment is still open.

Sorry I missed this! Done

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