[CD Taskbar] Move DisplayController method calls to BaseTaskbarContext

To ensure consistent, controllable Taskbar in Connected Displays Behavior, move all independent calls to the singleton DisplayController's various methods into one place in BaseTaskbarContext, where we have access to the parent context and can override default behaviors of these methods throughout taskbar if in external display.

Flag: EXEMPT not adding new behavior
Bug: 401553128
Test: m
Change-Id: If9efc0cfc18bac3ee75bb64bf5280ea979d1faa2