Support local dereferencing of `$ref` to `$anchor`

[mattpolzin]

Currently, local dereferencing only supports looking up in the Components Object.

This depends on other upcoming work that will expand JSONReference.InternalReference to support anchors in addition to components and paths.

[mattpolzin]

In preparation for a v4.0.0 release, I am bumping this issue to the v5.x milestone.