For searching multiple tabs, we need a way to show which tabs have a search
result, but we still need to be able to show which tab is active. Also, multiple
tabs can be highlighted, so that argument needs be be a bitfield enum. This
requires giving extra arguments to ui_item_enum_expand_tabs.

Unforunately this adds a bit of ugly complexity to this function. It would be
better if RNA enum items could have an "active" flag, but that change would
probably have larger scope.