Clip display blocks in the topology pane

Prevent display blocks from overflowing outside the pane when dragged.

Flag: com.android.settings.flags.display_topology_pane_in_display_list
Bug: b/352650922
Test: drag a display block so that it would overflow outside the pane
Change-Id: I326cb28f06914f71535906a0ce3e8fc04a4cb4f3

res/layout/display_topology_preference.xml

@@ -29,6 +29,7 @@
         android:src="@drawable/display_topology_background"/>
     <FrameLayout
         android:id="@+id/display_topology_pane_content"
+        android:clipToOutline="true"
         android:layout_width="match_parent"
         android:layout_height="match_parent"/>
     <TextView