Instead of iterating over the bindings, iterate over the base
objects that are snapshottable. This allows us to snapshot
base objects that are not bindings. In addition this refactors
the InternalFieldInfo class to eliminate potential undefined
behaviors, and renames it to InternalFieldInfoBase.
The {de}serialize callbacks now expect a InternalFieldInfo struct
nested in Snapshotable classes that can be used to carry
serialization data around. This allows us to create structs
inheriting from InternalFieldInfo for Snapshotable objects
that need custom fields.