Handle special case slices

Create a handler for any slice that doesn't include anything
from a PreferenceController.

Test: robotests
Change-Id: If23947152d61877537d0cac6240e96b9ab977bce
Bug: 80263568

src/com/android/settings/slices/SlicesFeatureProvider.java

@@ -28,6 +28,8 @@ public interface SlicesFeatureProvider {
      */
     void indexSliceData(Context context);
 
+    CustomSliceManager getCustomSliceManager(Context context);
+
     /**
      * Gets new WifiCallingSliceHelper object
      */