DM-47769: Refactor Wobbly schema to support Pydantic

[rra]

Instead of writing an explicit object conversion function, rework the Wobbly schema so that ORM objects can be converted directly to Pydantic objects using model_validate. This requires moving the ordering of results into the ORM rather than doing it manually, moving the error attributes into a table and allowing more than one error, and reworking the schema for results to avoid an autogenerated key that clashes with the client-provided result ID.

UWS does not allow multiple errors in the current schema, but any revision of the standard should ideally support multiple errors. For now, we can follow the convention of storing at most one error and not use this schema functionality, but since it makes the Pydantic integration easier, it seemed better to future-proof now.

Change the cascade configuration of the job ORM model to ensure that any orphaned result or error objects are deleted, which was already required by the schema.

[rra]

This is required to use the new Safir pagination support, since it requires direct conversion to a Pydantic model. (And really I should have done it this way all along. I was just lazy and copied the pattern from vo-cutouts.