Rollup merge of #108189 - compiler-errors:non_lifetime_binders-bound-stuff, r=jackh726

Fix some more `non_lifetime_binders` stuff with higher-ranked trait bounds

1. When assembling candidates for `for<T> T: Sized`, we can't ICE because the self-type is a bound type.
2. Fix an issue where, when canonicalizing in non-universe preserving mode, we don't actually set the universe for placeholders to the root even though we do the same for region vars.
3. Make `Placeholder("T")` format like `T` in error messages.

Fixes #108180
Fixes #108182

r? types

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -735,7 +735,10 @@ pub trait PrettyPrinter<'tcx>:
                     p!(print(data))
                 }
             }
-            ty::Placeholder(placeholder) => p!(write("Placeholder({:?})", placeholder)),
+            ty::Placeholder(placeholder) => match placeholder.name {
+                ty::BoundTyKind::Anon(_) => p!(write("Placeholder({:?})", placeholder)),
+                ty::BoundTyKind::Param(_, name) => p!(write("{}", name)),
+            },
             ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
                 // We use verbose printing in 'NO_QUERIES' mode, to
                 // avoid needing to call `predicates_of`. This should