Summary:
This diff creates the `dagster-graphql-client` CLI:

        1. Adds BK checks to ensure that current GraphQL queries by the client are included in a legacy query `query_snapshot` folder via `dagster-graphql-client query check`
                a. It also adds the `dagster-graphql-client query snapshot` command to add the GraphQL client's queries to the `query_snapshot` directory
        2. Tests to ensure that each query in the `client_backcompat` directory is still supported by the GraphQL server (so at a minimum, we can be intentional about breaking changes that arise)

Depends on D7409

Test Plan: bk script checks + new backcompat tests (this diff is mostly tests)

Reviewers: rexledesma, alangenfeld, catherinewu, sandyryza

Reviewed By: rexledesma

Differential Revision: https://dagster.phacility.com/D7421