Support Extending TypeSystems

[JacobHayes]

Is your feature request related to a problem? Please describe.

Some TypeSystems will overlap (eg: pydantic is an extension of python; pandas types are an extension of numpy ones). When these overlap, we often just hard code references to the other TypeSystem instance in the TypeAdapter code. This is a bit "brittle" because sometimes we want to convert both the base types + extended types.

Describe the solution you'd like

Add a TypeSystem "extends" (or similarly named) field that points to other TypeSystem to inherit from. For example, pydantic_type_system = TypeSystem(key="pydantic", extends=[python_type_system]). Then, to_{artigraph,system} would first check its own TypeAdapters before falling back to the extended systems' adapters.

Then, we'll need to pass the "root" TypeSystem around into the TypeAdapters and use that instead of any hard coded references to TypeSystems; replacing those hard coded references with extends in their TypeSystem.

Describe alternatives you've considered

The pydantic_type_system works around this / a similar issue when converting nested models by registering a _PythonBaseModelAdapter on the python_type_system - this allows us to just call python_type_system when converting from the pydantic BaseModelAdapter to handle both python natives + sub-models. Instead, we could have the pydantic_type_system extend python natively and then letself.type_system in the Pydantic TypeAdapters handle the extension.