Show topology pane detached from mirror toggle

Remove the extra blue border from the topology pane and give the toggle
below it its own rounded corners.

Flag: com.android.settings.flags.display_topology_pane_in_display_list
Test: screenshots
Test: verify display blocks are still clipped to the topology holder view
Bug: b/396116157
Change-Id: I3c0f826db24e5c599c6b51f71d099976fb04cbf0