Rollup merge of #104595 - compiler-errors:poly-existential-predicate, r=lcnr

Add `PolyExistentialPredicate` type alias

Wrapping `ExistentialPredicate`s in a binder is very common, and this alias already exists for the `PolyExistential{TraitRef,Projection}` types.

compiler/rustc_const_eval/src/util/type_name.rs

@@ -74,7 +74,7 @@ impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
 
     fn print_dyn_existential(
         self,
-        predicates: &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
+        predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
     ) -> Result<Self::DynExistential, Self::Error> {
         self.pretty_print_dyn_existential(predicates)
     }