[clang] [llvm] [coroutine] Implement llvm.coro.await.suspend intrinsic (PR #79712)

[Chuanqi Xu via cfe-commits]

https://github.com/ChuanqiXu9 commented:

Thanks. This looks much better now.

Given the CoroAwaitSuspendInst is lowered before splitting coroutines, I think we don't need to handle it specially in `CoroSplit` any more.

https://github.com/llvm/llvm-project/pull/79712