feat(obj) add lv_obj_move_to_index(obj, index), renamed lv_obj_get_child_id(obj) to lv_obj_get_index(obj) (#2514)

* - renamed lv_obj_get_id(obj) to lv_obj_get_index(obj).

- added lv_obj_move_to_index(obj, index).

* automatic review comment fixed

* removed unused variable

* review issue

* restored deprecated function in header, otherwise Build Micropython with LVGL submodule / build (pull_request)  failes

* moved deprecated lv_obj_get_child_id() back to lv_obj_tree.h, otherwise Micropython will not build

* inline function did not work

* made deprecated function 'static inline'

* and now also inline

* move static inline function to lv_api_map.h again

* removed lv_obj_move_up/down

* changed log to warning for deprecated function

* redefined lv_obj_move_foreground(obj) and lv_obj_move_background(obj) as inline functions now calling lv_obj_move_to_index(obj, index).

- lv_obj_swap(obj1, obj2) added. (#2461)

examples/widgets/win/lv_example_win_1.c

@@ -5,7 +5,7 @@
 static void event_handler(lv_event_t * e)
 {
     lv_obj_t * obj = lv_event_get_target(e);
-    LV_LOG_USER("Button %d clicked", lv_obj_get_child_id(obj));
+    LV_LOG_USER("Button %d clicked", lv_obj_get_index(obj));
 }
 
 void lv_example_win_1(void)