Check all tasks for good intent launch when creating channels

When creating a notification channel, call into the ActivityTaskManager
to determine if there are any valid tasks to show a permission prompt
over. Creates the method in ActivityTaskManagerInternal to support this.

Bug: 17047250
Test: atest NotificationPermissionTest
Change-Id: I7b2b6a42101607b1eaa25f108760cc2449661499
7 files changed