Use thirdparty subsystem and core model legacy test controllers

This moves the core-model-test and susbsystem-test legacy controllers to a separate repository at https://github.com/wildfly/wildfly-legacy-test.

Benefits are that the 7.1.2 and 7.2.0 dependencies no longer clutter up the classpath, and that we can add more controllers as needed.

7.1.2 core controllers are enabled using -Djboss.test.transformers.core.old 
7.1.2. subsystem controllers are enabled using -Djboss.test.transformers.subsystem.old (I think this is already in master and not part of this commit)