Make activemq dependency on cli module optional

Dependency on org.jboss.as.cli from org.wildfly.extension.messaging-activemq should be made optional.

At runtime, the commands are not loaded on the server side. They are loaded thanks to ServiceLoader from CLI, so if CLI is present, the commands are in use, otherwise they are un-used.

We would observe a gain of 2.3+MB in filesystem footprint when a server without CLI is provisioned.