Create NotificationListController

Move a few things from NotificationEntryManager into it.

This class will (hopefully) eventually replace *NotificationPresenter
as the main "controller" class for the notification shade. This will
allow us to centralize all of our universal controller code into one
place. The controller defer certain method calls to platform-specific
objects (what remains of the NotificationPresenters).

Test: atest
Change-Id: Ic729014f1bef825b635ced86ffb825b5734ad562