[CD Settings] Fetch logicalSize from DisplayManager

To support display stacking in mirroring mode pane, we'll have to fetch
display logicalSize for displays that are not in topology (mirrored
displays).

This includes small refactoring and cleanup to simplify applyTopology().
The logic change is only to fetch the logical display size

Bug: 401059862
Test: atest DisplayTopologyPreferenceTest
Flag: com.android.settings.flags.display_topology_pane_in_display_list

Change-Id: I4977aac369b615f144a874cfa33101d6bf920273