Represents the circular side of a bi-directional entity fetch. Wraps a reference to an EntityReference
as an EntityFetch. We can use the special type as a trigger in AliasResolutionContext, etc to lookup information
based on the wrapped reference.
This relies on reference lookups against the EntityReference instances, therefore this allows representation of the
circularity but with a little protection against potential stack overflows. This is unfortunately still a cyclic
graph. An alternative approach is to make the graph acyclic (DAG) would be to follow the process I adopted in the
original HQL Antlr v3 work with regard to always applying an alias to the "persister reference", even where that
meant creating a generated, unique identifier as the alias. That allows other parts of the tree to refer to the
"persister reference" by that alias without the need for potentially cyclic graphs (think ALIAS_REF in the current
ORM parser). Those aliases can then be mapped/catalogued against the "persister reference" for retrieval as needed.