Rollup merge of #141932 - azhogin:azhogin/async-drop-inside-asyncgen-fix, r=oli-obk

Fix for async drop inside async gen fn

Return value (for yield) is corrected for async drop inside async gen function.
In CFG, when internal async drop future is polled and returned `Poll<()>::Pending`, then async gen resume function returns `Poll<(OptRet)>::Pending`.

Fixes rust-lang/rust#140530

tests/ui/async-await/async-drop/assign-incompatible-types.rs

@@ -1,7 +1,8 @@
-//@ known-bug: #140530
+// ex-ice: #140530
 //@ edition: 2024
-
+//@ build-pass
 #![feature(async_drop, gen_blocks)]
+#![allow(incomplete_features)]
 async gen fn a() {
   _ = async {}
 }