Do not expose Infinispan bits to deployments importing the Hibernate main module

This is mainly a follow up to
https://bugzilla.redhat.com/show_bug.cgi?id=1202911

But also a consequence of difficulties I had with Hibernate Search (which depends on both latest Infinispan and the Hibernate version in WildFly), and Hibernate OGM (which requires Hibernate ORM but has strong coupling with specific versions of Infinispan).

The gist of the problem is that the module org.hibernate:main includes the integration code with Infinispan for second level caching.

While I agree people will want to enable the second level caching, I don't think they should be exposed to it, so I'll propose some changes.