ScriptTextEditor Fix checking if script is attached to any node belonging to scene

[kleonc]

Fixes #66209.

_find_script_node function was not traversing children not owned by the given scene so nodes added in the given scene to a subscene's root / its editable children weren't reached and thus their scripts were not checked. Now it traverses all children but checks the scripts only for the nodes owned by the given scene.

The changed _find_script_node function is used only for this check so it shouldn't break anything:

godot/editor/plugins/script_text_editor.cpp

Lines 1567 to 1571 in 7476569

	Node *sn = _find_script_node(scene_root, scene_root, script);
	if (!sn) {
	EditorNode::get_singleton()->show_warning(vformat(TTR("Can't drop nodes because script '%s' is not used in this scene."), get_name()));
	return;
	}

[akien-mga]

Thanks!

[akien-mga]

Cherry-picked for 3.6.

[timothyqiu]

Cherry-picked for 3.5.2