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)

src/lv_api_map.h

@@ -41,6 +41,46 @@ static inline LV_ATTRIBUTE_TIMER_HANDLER uint32_t lv_task_handler(void)
  *      MACROS
  **********************/
 
+
+/**********************
+ * INLINE FUNCTIONS
+ **********************/
+
+/**
+ * Move the object to the foreground.
+ * It will look like if it was created as the last child of its parent.
+ * It also means it can cover any of the siblings.
+ * @param obj       pointer to an object
+ */
+static inline void lv_obj_move_foreground(lv_obj_t* obj)
+{
+    lv_obj_t* parent = lv_obj_get_parent(obj);
+    lv_obj_move_to_index(obj, lv_obj_get_child_cnt(parent) - 1);
+}
+
+/**
+ * Move the object to the background.
+ * It will look like if it was created as the first child of its parent.
+ * It also means any of the siblings can cover the object.
+ * @param obj       pointer to an object
+ */
+static inline void lv_obj_move_background(lv_obj_t* obj)
+{
+    lv_obj_move_to_index(obj, 0);
+}
+
+
+
+/**********************
+ * DEPRECATED FUNCTIONS
+ **********************/
+
+static inline uint32_t lv_obj_get_child_id(const struct _lv_obj_t* obj)
+{
+    LV_LOG_WARN("lv_obj_get_child_id(obj) is deprecated, please use lv_obj_get_index(obj).");
+    return lv_obj_get_index(obj);
+}
+
 #ifdef __cplusplus
 } /*extern "C"*/
 #endif