Displaying the labels tip immediately feels too intrusive,
make this work more like regular tooltips, displaying more quickly.
Tooltips can now uses multiple passes, each pass with it's own delay
for the next pass to show.
Move timer and tip out of button code,
now the only requests a tooltip,
passing a creation callback to run.
Needed for manipulators in 2.8,
also helps de-duplicate logic - since we never want
multiple tool-tips showing at once.
