Revert^2 "Fix binder error when an app has many channels"

34b3e4b5

Test: NotificationChannelGroupTest
Test: NotificationManagerServiceTest
Test: PreferencesHelperTest (new test for revert:
testGetNotificationChannelGroup)
Test: long press on a conversation notification in the shade
Bug: 215072888

Change-Id: Ib9c671b0fd1f97e01ef02957839ebad2cadb5e44