Support connecting noodle to another node and ensure it

stays connected when parent node moves

include/ui.h

@@ -38,10 +38,16 @@ struct ui_elem_colours {
   colour border;
 };
 
+typedef struct ui_noodle_elem ui_noodle_elem;
+struct ui_noodle_elem {
+  line noodle;
+  u64 connected_node;
+};
+
 typedef struct ui_node_elem ui_node_elem;
 struct ui_node_elem {
   rect rec;
-  line *noodles;
+  ui_noodle_elem *noodles;
   u64 inputs;
 };