Centralize retained popup activation

src/node_combobox.cpp

@@ -76,10 +76,7 @@ void NodeComboBox::loaded()
         popup->SetFlexGrow(1.f);
         popup->update();
         root()->update();
-        popup->mouse_capture();
-        popup->m_mouse_ignore = false;
-        popup->m_flood_events = true;
-        popup->m_capture_children = false;
+        pp::panopainter::activate_legacy_popup_overlay(*popup);
     };
 }