Add GraphQL cql-first data aggregations

[polandll]

per stargate/stargate#901

[polandll]

EXAMPLE:

query maxSubscription {
      mdsubscriptions(value: { cid: 1, sid: "sheth" }) {
        values {
          cid
          sid
          rtime
          uic
          max: _int_function(name: "max", args: ["uic"])
    }
  }
}

[polandll]

https://github.com/stargate/stargate/blob/master/testing/src/main/java/io/stargate/it/http/graphql/cqlfirst/AggregationFunctionsTest.java#L227

[polandll]

example:
query get_nb_thread_for_AAA {
message (value: {thread_id:"AAA"}) {
values {
c: _bigint_function(name: "count", args: ["message_id"])
}
}
}