Auto merge of #124662 - zetanumbers:needs_async_drop, r=oli-obk

Implement `needs_async_drop` in rustc and optimize async drop glue

This PR expands on #121801 and implements `Ty::needs_async_drop` which works almost exactly the same as `Ty::needs_drop`, which is needed for #123948.

Also made compiler's async drop code to look more like compiler's regular drop code, which enabled me to write an optimization where types which do not use `AsyncDrop` can simply forward async drop glue to `drop_in_place`. This made size of the async block from the [async_drop test](67980dd6fb/tests/ui/async-await/async-drop.rs) to decrease by 12%.

compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs

@@ -845,7 +845,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
             | ty::Str
             | ty::Slice(_)
             | ty::Tuple(_)
-            | ty::Error(_) => self_ty.async_destructor_ty(ecx.interner(), goal.param_env),
+            | ty::Error(_) => self_ty.async_destructor_ty(ecx.interner()),
 
             // We do not call `Ty::async_destructor_ty` on alias, param, or placeholder
             // types, which return `<self_ty as AsyncDestruct>::AsyncDestructor`