Create ForceEagerSessionCreationFilter

[rwinch]

Currently Spring Security's SecurityContextPersistenceFilter has two tasks:

• (optionally) eagerly create sessions
• Using the SecurityContextRepository to load/save the SecurityContext

We should decouple these two tasks by creating a new ForceEagerSessionCreationFilter. The decoupling is especially important to support deprecation and removal of SecurityContextPersistenceFilter in favor of SecurityContextHolderFilter.