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/extra/themes/default/lv_theme_default.c

@@ -630,13 +630,13 @@ static void theme_apply(lv_theme_t * th, lv_obj_t * obj)
 
 #if LV_USE_WIN
         /*Header*/
-        if(lv_obj_get_child_id(obj) == 0 && lv_obj_check_type(lv_obj_get_parent(obj), &lv_win_class)) {
+        if(lv_obj_get_index(obj) == 0 && lv_obj_check_type(lv_obj_get_parent(obj), &lv_win_class)) {
             lv_obj_add_style(obj, &styles->bg_color_grey, 0);
             lv_obj_add_style(obj, &styles->pad_tiny, 0);
             return;
         }
         /*Content*/
-        else if(lv_obj_get_child_id(obj) == 1 && lv_obj_check_type(lv_obj_get_parent(obj), &lv_win_class)) {
+        else if(lv_obj_get_index(obj) == 1 && lv_obj_check_type(lv_obj_get_parent(obj), &lv_win_class)) {
             lv_obj_add_style(obj, &styles->scr, 0);
             lv_obj_add_style(obj, &styles->pad_normal, 0);
             lv_obj_add_style(obj, &styles->scrollbar, LV_PART_SCROLLBAR);