In MDL-72397, I have deprecated question_category_list and question_category_item, which were the only remaining usages of the moodle_list and list_item abstract classes from listlib. I also deprecated the moodle_list::display_page_numbers method as this was relying on the QUESTION_PAGE_LENGTH constant, which is defined in the question_category_object class file, and that has been deprecated too.

Given there are no more usages in core, this might be a good time to deprecate the listlib classes entirely?