• highlight should only be triggered on mouse down, as that is the point of interaction with an item which indicates it is "in use"; a mouse-up event cannot occur on an item which has not previously received a mouse-down event, so toggling this on mouse-up will be wrong/duplicated 100% of the time
• unhighlight should only be triggered during mouse-up events if the list is in no-select mode, as it will otherwise be implicitly during selection if necessary

this should ensure that these events are emitted exactly one time and correctly
for each click event
Depends on D10516