Snooze API tests for notification listeners and assistants.

Bug: 150629389
Test: atest android.app.notification.legacy29.cts.NotificationAssistantServiceTest\#testOnNotificationSnoozedUntilContext
Test: atest android.app.notification.legacy29.cts.NotificationAssistantServiceTest\#testUnsnoozeFromNAS
Change-Id: Ie949821fcf1192efe8b6b3e95c9daca71347b11e
3 files changed