Remove Dauphin
Summary: This makes it easier to reuse pieces of the dagster-graphql schema, as well as smoothing the path for new contributors. Resolves https://github.com/dagster-io/dagster/issues/2270.
Test Plan: Unit
Reviewers: alangenfeld, prha, schrockn, dgibson, johann
Reviewed By: dgibson
Subscribers: schrockn
Differential Revision: https://dagster.phacility.com/D6164