[crag] Add validation step to default config buildup for to_job.
Summary: We previously weren't doing any validation of config in to_job. This adds validation, and also carries over all fields from old config document.
Test Plan: added unit test to ensure config mistakes are caught.
Reviewers: sandyryza, alangenfeld
Reviewed By: alangenfeld
Differential Revision: https://dagster.phacility.com/D9190