Centralize retained combo overlay insertion

src/node_combobox.cpp

@@ -1,6 +1,7 @@
 #include "pch.h"
 #include "log.h"
 #include "node_combobox.h"
+#include "legacy_ui_overlay_services.h"
 #include "node_popup_menu.h"
 
 Node* NodeComboBox::clone_instantiate() const
@@ -24,11 +25,12 @@ void NodeComboBox::loaded()
     m_text->set_text(m_data[m_current_index].c_str());
     m_selected_child_index = m_current_index;
     on_click = [this](Node* target) {
-        NodePopupMenu* popup = new NodePopupMenu;
+        auto popup = std::make_shared<NodePopupMenu>();
+        popup->set_manager(m_manager);
         popup->init();
         popup->create();
         popup->loaded();
-        root()->add_child(popup);
+        (void)pp::panopainter::attach_legacy_overlay_node_to_root(*this, popup);
         m_items.clear();
         for (int i = 0; i < m_data.size(); i++)
         {