Support June 2023 incremental delivery spec
`@defer`/`@stream` [are experimentally supported by Apollo Server V4](https://www.apollographql.com/docs/apollo-server/workflow/requests/#incremental-delivery-experimental).

But the [June 2023 spec](https://github.com/graphql/defer-stream-wg/discussions/69) is not yet supported.

Ideally, the server could respond in either format based on the value of `deferSpec` provided by the client: `deferSpec=20220824` or `deferSpec=20230821`, which was set up nicely to support such a situation.

A switchable response format would allow both Apollo and urql clients to use incremental delivery, as urql [has upgraded](https://github.com/urql-graphql/urql/pull/3389) to the new spec.
