Serializer should only serialize user defined AdvancedExternalizers

ISPN-10727 Is caused because the Serialization configuration is deemed to have been modified by a user in the test setup. However, the classes being serialized are the internal Externalizers that are defined in various modules ModuleLifecycle implementations and are of no significance to the user, as they will always be applied regardless of the xml configuration. Therefore, we should hide all internal Externalizer classes from the user.