Refactor managers that defer notification removal

This CL introduces NotificationLifetimeExtender, an interface for the
various notification managers to implement to say that a notification
should stay around even after being removed.  This provides greater
consistency/standardization as opposed to having the same
implementation done differently and scattered throughout different
classes.

Also implements small refactors to try to reduce coupling where possible
(in particular reduce references to NotificationEntryManager) and move
logic to more appropriate locations (in particular move a lot of remote
input logic from NotificationEntryManager to
NotificationRemoteInputManager.)

Test: manual (see below); runtest systemui
* heads up + cancel
* guts active + cancel
* ambient pulse + cancel (UI here is janky even on master)
* have a remote input active + cancel
* have remote history, send, see that the notification stays
Change-Id: I24d345a1f2d8751827e367d1432918b3db7fa5f3