Rollup merge of #55778 - nnethercote:LrcPreds, r=eddyb

Wrap some query results in `Lrc`.

So that the frequent clones in `try_get` are cheaper.

src/librustdoc/clean/mod.rs

@@ -1563,7 +1563,7 @@ impl Clean<Generics> for hir::Generics {
 }
 
 impl<'a, 'tcx> Clean<Generics> for (&'a ty::Generics,
-                                    &'a ty::GenericPredicates<'tcx>) {
+                                    &'a Lrc<ty::GenericPredicates<'tcx>>) {
     fn clean(&self, cx: &DocContext) -> Generics {
         use self::WherePredicate as WP;