[clang] [llvm] [Coroutines] Never collect return value alloca into coroutine frame (PR #213580)

[Weibo He via cfe-commits]

NewSigma wrote:

> > In the middle end, remove the assumption that an address can cross suspension points if missing lifetime.end markers.
> 
> I feel using lifetime markers to control whether or not to put something into the frame, is implicit. It will be better to use an explicit way. e.g., if we don't want metadata, can we introduce an intrinsic?

Sounds good.

https://github.com/llvm/llvm-project/pull/213580