SelectionTool/Listbox: Fix in calculating the start of last page in selection
as the comment (which is removed now) said:
XXX: This method is broken, since "total_size" field is not
present in the listbox rendering any longer. It should be
removed.Also:
- make sure that Listbox always knows how many lines are to be displayed.
- add testPagerWithCustomListMethod in listbox_zuite of erp5_ui_test, which checks that listbox jumping to previous/next/first/last works correctly for a list method that returns only the elements that the listbox is to render.