Set up stubs for SchemaBlueprint

[tninesling]

Begin porting blueprints from JS. The JS version extends FederationBlueprint from SchemaBlueprint. With this setup, we'll have to call the DefaultBlueprint from the FederationBlueprint in lieu of super.

Omitted validationRules(): readonly SDLValidationRule[] because apollo-rs doesn't allow passing in a set of rules to validate in the same way as graphql-js. Additionally, type signatures using GraphQLError or GraphQLError[] use FederationError, which can represent multiple errors. The JS code marks success with an empty error array, so I've used Result<(), FederationError> for GraphQLError[].

JS SchemaBlueprint: https://github.com/apollographql/federation/blob/main/internals-js/src/definitions.ts#L891
JS FederationBlueprint: https://github.com/apollographql/federation/blob/main/internals-js/src/federation.ts#L1549

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Build ID: 1fb6886890b24bf2b93b82cb

[tninesling]

General question: should we be operating on apollo_compiler::Schema here, apollo_federation::schema::FederationSchema, or is this where we'll introduce the staged schema type we talked about during the kickoff?