[llvm] [Coroutines] Allocas used after @coro.end should not go in the coro frame (PR #127524)

[Hans Wennborg via llvm-commits]

zmodem wrote:

Thinking more about this makes me unsure whether it's correct. It's putting a lot of faith in that [note in SpillUtils.cpp](https://github.com/llvm/llvm-project/blob/9d487050a144b895950a6fd48b993513a714e69d/llvm/lib/Transforms/Coroutines/SpillUtils.cpp#L367), but I'm not sure that the semantics of the coro intrinsics really support my conclusion?

Clang knows exactly what's going on with these parameters, and since I found https://llvm.org/docs/Coroutines.html#coro-outside-frame-metadata, I think we can just apply that to exclude them from the frame.

Please see #127653 for what I think is a better fix.

https://github.com/llvm/llvm-project/pull/127524