Introduce NotificationInsetsController.

Allow Notification Shade Window view's insets be calculated by a
separate module. OEMs can override this module and provide their own
calculation logic.
Bug: 251207888
Test: Build
Change-Id: Ia0b6f854dc62eca4bed5c4a893f8277accf0696c

Change-Id: I07ecf6742de791839c756beadcd1c1399453bd8b