Restrict apps from dismissing UIJ notifications.

Apps should not be able to dismiss notifications associated with
user-initiated jobs nor should they be able to delete the associated
notification channel.

Bug: 269533590
Test: atest NotificationManagerTest
Test: atest NotificationManagerServiceTest
Test: atest ServiceTest
Test: atest NotificationChannelTest
Test: atest NotificationTest
Test: atest JobNotificationCoordinatorTest
Change-Id: I59d95120b3722ed8cb6675ed89576b05de5e6092