Fix clickable notification row elements

- Don't mark notification guts as clickable. Originally they were marked
as clickable so that the guts wouldn't send touches to trigger the
ExpandableNotificationRow's click, NotificationClicker. This caused
talkback to speak "Double-tap to activate" when announcing the
NotificationGuts even though double-tapping would do nothing.
- Instead, added logic in NotificationClicker to ignore clicks that
occur when the guts are exposed.

Test: manual
Fixes: 140398522
Change-Id: I806051ffd43ed27c38e804fdc43e2c2d3522566c