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/NotificationPreferenceController.java

@@ -184,4 +184,11 @@ public abstract class NotificationPreferenceController extends AbstractPreferenc
     protected boolean hasValidGroup() {
         return mChannelGroup != null;
     }
+
+    protected final boolean isDefaultChannel() {
+        if (mChannel == null) {
+            return false;
+        }
+        return Objects.equals(NotificationChannel.DEFAULT_CHANNEL_ID, mChannel.getId());
+    }
 }