[clang] [llvm] [Coroutines] Introduce [[clang::coro_only_destroy_when_complete]] (PR #71014)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

Didn't dig into the LLVM section of this, but the CFE section looks good delta some small documentation changes.

https://github.com/llvm/llvm-project/pull/71014