Add 'Snooze' to local context menu for notifications

Bug: 34840333
Test: manual - 1. turn talkback on
               2. have a notification focused
               3. invoke local context menu, note that 'snooze' is an option
               4. select snooze, note that notification is snoozed

Change-Id: Id3ea62a0a9e5c2b8893aa5b548e64bb2b341d7a2