Reduced down slop and added action for expanding notifications (1/2)

Added an option to select expanding notifications to execute after a
gesture. Exploring swipe down by reducing the touch slope to a smaller
value to execute more. Since it is swiping towards the edge, less events
will be received and typically hard to trigger when swiping other
directions.

Bug: 112934365
Test: manual
Change-Id: I6a854043183d85b43d32633c5fbe88262f473012