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

[Chuanqi Xu via cfe-commits]

================
@@ -5038,6 +5038,8 @@ class CoroutineSuspendExpr : public Expr {
   OpaqueValueExpr *OpaqueValue = nullptr;
 
 public:
+  enum SuspendReturnType { SuspendVoid, SuspendBool, SuspendHandle };
----------------
ChuanqiXu9 wrote:

nit: Add a comment to explain that the return type of coroutines can only be one of them. Also I prefer `enum class` style.

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