Make some display related slices public.

Only PreferenceControllers with isPublicSlice() set to true are exposed
to other apps. Others will be Settings only.

Bug: 141088937
Test: robotests
Change-Id: I2a36da4ac4bb14a4d2ac7b89ab2bb3ebf8e655f7

src/com/android/settings/display/NightDisplayActivationPreferenceController.java

@@ -63,6 +63,11 @@ public class NightDisplayActivationPreferenceController extends TogglePreference
         return TextUtils.equals(getPreferenceKey(), "night_display_activated");
     }
 
+    @Override
+    public boolean isPublicSlice() {
+        return true;
+    }
+
     @Override
     public void displayPreference(PreferenceScreen screen) {
         super.displayPreference(screen);