JSON Schema equivalence tests

[samuelcolvin]

The whole point of FastUI is that we give some level of guarantee that the Pydantic models in the backend match the TS interfaces in the react app, but currently there's no test to catch if that's not the case.

To check consistency, we should generate JSON Schema for the component props interfaces, and for the pydantic models, and check they match. There will probably need to be some edge cases skipped or specially accounted for.

The tests should be written in Python, as little code as possible should be in node/ts.