It was used to position the text in one line text areas where the label is shorter then the text area itself.
However, setting min_width=100% in case of one line text area ensures that the label is at least as wide as
the text area. This way the normal text_align style property can be used too.
Fixes https://forum.lvgl.io/t/spinbox-text-centering-not-working-as-intended-expected/6762/4
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/
