Notably, this is missing the equality checking because ST introduces a new type called "ModelBackedItem", which is specifically a type backed by a DictionaryBase item, with extensions. It is very similar to a Wrapper, but has different common utility. If there is a way to migrate that here, then the equality methods can come here as well.
This change looks dramatic, but it's just separating out the already-split namespaces into separate top-level folders. In theory, every single one could be built into their own Nuget package. `SabreTools.Serialization` still builds the normal Nuget package that is used by all other projects and includes all namespaces.
