Extract top-ui logic into TopUiController

Currently, NotificationShadeWindowController acts as the central entity
to handle top-ui requests. This CL extracts that logic into a standalone
TopUiController. Components that need to request top-ui do not have to
inject NotificationShadeWindowController anymore in the future, but can
directly use TopUiController instead.

As a first step, TopUiController is introduced behind a refactor flag.
For now, all components must check the flag value to decide where to
request top-ui. If the refactor flag is enabled, the request needs to be
sent to TopUiController. Otherwise the request needs to be sent to
NotificationShadeWindowController.

Once the flag reaches nextfood, all components using top-ui can be
refactored to use TopUiController only.

Bug: 411061512
Test: TopUiControllerImplTest
Flag: com.android.systemui.enable_top_ui_controller
Change-Id: I7113ad66275f2da5d350a5829f91ce5deec66f4e