Rollup merge of #124382 - petrochenkov:itemvisit, r=lcnr

ast: Generalize item kind visiting

And avoid duplicating logic for visiting `Item`s with different kinds (regular, associated, foreign).

The diff is better viewed with whitespace ignored.

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -1335,7 +1335,7 @@ impl<'a, 'b, 'tcx> Visitor<'b> for BuildReducedGraphVisitor<'a, 'b, 'tcx> {
         }
 
         self.build_reduced_graph_for_foreign_item(foreign_item);
-        visit::walk_foreign_item(self, foreign_item);
+        visit::walk_item(self, foreign_item);
     }
 
     fn visit_block(&mut self, block: &'b Block) {