Fixes 3 problems with deselecting items in an autocomplete field:

1. Keep track of whether items were in the offical suggestion list, or are newly created
   tags and remove the "newly created tags" from the suggestion list when they are
   deselected
2. Change the aria-role for the selected items list when items cannot be deselected (and
   do not treat it like a multiselect list).
3. When leaving and returning focus to the selected items list, remember the last
   active-descendant.