Add simple async drop glue generation

Explainer: https://zetanumbers.github.io/book/async-drop-design.html

https://github.com/rust-lang/rust/pull/121801

compiler/rustc_monomorphize/src/collector.rs

@@ -973,6 +973,7 @@ fn visit_instance_use<'tcx>(
             }
         }
         ty::InstanceDef::DropGlue(_, Some(_))
+        | ty::InstanceDef::AsyncDropGlueCtorShim(..)
         | ty::InstanceDef::VTableShim(..)
         | ty::InstanceDef::ReifyShim(..)
         | ty::InstanceDef::ClosureOnceShim { .. }