Rollup merge of #85800 - BoxyUwU:const-param-default-diagnostics, r=oli-obk

Fix some diagnostic issues with const_generics_defaults feature gate

This PR makes a few changes:
- print out const param defaults in "lifetime ordering" errors rather than discarding them
- update `is_simple_text` to account for const params when checking if a type has no generics, this was causing a note to be failed to add to an error message
- fixes some diagnostic wording that incorrectly said there was ordering restrictions between type/const params despite the `const_generics_defaults` feature gate is active

compiler/rustc_middle/src/ty/diagnostics.rs

@@ -54,7 +54,7 @@ impl<'tcx> TyS<'tcx> {
     /// ADTs with no type arguments.
     pub fn is_simple_text(&self) -> bool {
         match self.kind() {
-            Adt(_, substs) => substs.types().next().is_none(),
+            Adt(_, substs) => substs.non_erasable_generics().next().is_none(),
             Ref(_, ty, _) => ty.is_simple_text(),
             _ => self.is_simple_ty(),
         }