Combines NotificationEntryManager listener interfaces (part 4).

This change combines the onEntryRemoved() and onNotificationRemoved()
methods on NotificationEntryListener to a single method.  The logic in
NotificationEntryManager which calls these methods is rearranged and a
flag is added to the callback method in order to fully preserve the
previous behavior of all implementors.

Test: atest SystemUITests, manual
Change-Id: I6077e78005ed6c20b02f5fa21f213199384cc3b8