feat(event, widgets) improve the paramter of LV_EVENT_DRAW_PART_BEGIN/END

Add lv_<widget>_draw_part_type_t to widgets to precisly describe the hooked drawings.
Also add class_p element to lv_obj_draw_part_dsc_t to show what widgets lv_<widget>_draw_part_type_t needs to be used.

Related to: https://forum.lvgl.io/t/how-to-add-minor-division-lines-to-a-chart/5366/

src/core/lv_obj_draw.c

@@ -330,6 +330,12 @@ void lv_obj_draw_dsc_init(lv_obj_draw_part_dsc_t * dsc, const lv_area_t * clip_a
     dsc->clip_area = clip_area;
 }
 
+bool lv_obj_draw_part_check_type(lv_obj_draw_part_dsc_t * dsc, const lv_obj_class_t * class_p, uint32_t type)
+{
+    if(dsc->class_p == class_p && dsc->type == type) return true;
+    else return false;
+}
+
 void lv_obj_refresh_ext_draw_size(lv_obj_t * obj)
 {
     LV_ASSERT_OBJ(obj, MY_CLASS);