ClassNotFoundException when loading Artemis transformer class.

The org.apache.activemq.artemis module has an optional dependency on a org.apache.activemq.artemis.addons that is meant to define classes that needs to be instantiated by Artemis (e.g. divert's transformers, server interceptors, etc.).

However the code that is instantiating classes from Artemis has been moved from the org.apache.activemq.artemis to the org.apache.activemq.artemis.journal module in WFLY-5522.

The optional dependency to org.apache.activemq.artemis.addons should set export to true so that its classes can be loaded by the org.apache.activemq.artemis.journal module.