HHH-8118 Create one OSGiClassLoader per persistence unit

Apologies for the huge PR...

This boiled down to wiring ClassLoaderService, ServiceRegistry, or BindingContext into dozens of sequences.  Once all class and resource loading are 100% reliant on ClassLoaderService, instead of static CL fixes, we'll be able to fully support one CL per unit.

In general, I tried to use BindingContext as much as possible within the metamodel sources.  Elsewhere, it made more sense to directly accept the CLS or SR.

Areas still needing work:

* org.hibernate.type. A few types do class lookups.

org.hibernate.cfg, org.hibernate.internal.util.xml, org.hibernate.mapping, etc. were ignored since they'll be removed or repurposed in 5.0.