Add custom serializer to config type snapshot
Summary: This makes the pipeline snapshot Id stable if you haven't made any changes to the run config.
Test Plan: BK, verify pipeline snapshot ID changes in https://dagster.phacility.com/D8550 no longer needed
Reviewers: cdecarolis, alangenfeld
Reviewed By: alangenfeld
Differential Revision: https://dagster.phacility.com/D9141