Optimize use of proxies for reference injection

The spec allows the following optimization to be put in place:

For certain combinations of scopes, the container is permitted to optimize the above procedure:

• The container is permitted to directly inject a contextual instance of the bean, as defined in Section 6.5.2.
• If an incompletely initialized instance of the bean is registered with the current CreationalContext, as defined in Section 6.1, the container is permitted to directly inject this instance.
  However, in performing these optimizations, the container must respect the rules of injectable reference validity.

Start by enumerating the set of allowed combinations of scopes.