Handle Keyboard long-presses and Talkback shortcut on notifications

An incremental improvement to keyboard support on the status bar.
SwipeHelper calls a method on ExpandableNotificationRow, which it then
manually invokes from keydown/ups and the AccessibilityAction shortcut.

Regular clicks on the lockscreen still do not activate the notification.

Bug: 34840327
Test: manual
Change-Id: I5b59dec26c5e20237c4136820fff902ff8221371