Home Controls: Add conditional copy for setting.

Add conditional copy for when allow trivial devices setting is disabled.
Add guidance on how to enable it.

Bug: 227344249
Test: Manual and unit test
Change-Id: I0f2f6dc933804ee6ba15dc180dc717d2a5b729a5

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

@@ -50,6 +50,9 @@ public class ControlsTrivialPrivacyPreferenceController extends TogglePreference
 
     @Override
     public CharSequence getSummary() {
+        if (getAvailabilityStatus() == DISABLED_DEPENDENT_SETTING) {
+            return mContext.getText(R.string.lockscreen_trivial_disabled_controls_summary);
+        }
         return mContext.getText(R.string.lockscreen_trivial_controls_summary);
     }