Ignore locked nodes when click selecting in 3d editor

When selecting 3d nodes with a single click, the node closest to the
camera is selected. If the closest node was locked, it would block the
selection, even when there was unlocked nodes behind the locked node.

This PR replaces the `_select_ray` method call used to find the closest
node with the similar `_find_items_at_pos` method, which can skip any
locked nodes.

Fixes #84764

editor/plugins/node_3d_editor_plugin.cpp

@@ -1918,12 +1918,17 @@ void Node3DEditorViewport::_sinput(const Ref<InputEvent> &p_event) {
 					}
 
 					if (after != EditorPlugin::AFTER_GUI_INPUT_CUSTOM) {
-						//clicking is always deferred to either move or release
-						clicked = _select_ray(b->get_position());
+						// Single item selection.
+						Vector<_RayResult> selection;
+						_find_items_at_pos(b->get_position(), selection, false);
+						if (!selection.is_empty()) {
+							clicked = selection[0].item->get_instance_id();
+						}
+
 						selection_in_progress = true;
 
 						if (clicked.is_null()) {
-							//default to regionselect
+							// Default to region select.
 							cursor.region_select = true;
 							cursor.region_begin = b->get_position();
 							cursor.region_end = b->get_position();