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

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

> There is substantial inconsistency between "coro only destroy when complete" and "... when done" throughout the PR (in various forms; e.g. literal strings, snake_case, CamelCase, ALL_CAPS as well as file names).
> 
> Presumably there should only be one spelling everywhere.

Done

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