Notification settings updates

- smaller icons
- text update
- fx header
- fix category header

Test: make -j RunSettingsRoboTests

Change-Id: If822d6db31a8dccf20ee88182cda1aee34aa7675
Fixes: 77325154
Fixes: 77323406
Fixes: 77324677
Fixes: 74408368

src/com/android/settings/notification/ImportancePreferenceController.java

@@ -58,7 +58,7 @@ public class ImportancePreferenceController extends NotificationPreferenceContro
         if (mChannel == null) {
             return false;
         }
-        return !NotificationChannel.DEFAULT_CHANNEL_ID.equals(mChannel.getId());
+        return !isDefaultChannel();
     }
 
     @Override