Add scoped overlay hosts

examples/bench_images.rs

@@ -31,7 +31,7 @@ impl DefaultAppState for State {
             .ui
             .widgets
             .add_strong(ScrollArea::new(span.any(), Axis::Y, Pin::End));
-        ui_state.set_root(root.any());
+        ui_state.set_root(rsc, root.any());
         Self {
             ui_state,
             span: span_weak,

examples/message_list.rs

@@ -79,7 +79,7 @@ impl DefaultAppState for State {
             .masked()
             .background(rect(PaintId::WHITE))
             .add_strong(rsc);
-        ui_state.set_root(root.any());
+        ui_state.set_root(rsc, root.any());
 
         Self { ui_state }
     }