Enable @requires on root Query types or error on using on root query types

[lleadbet]

Issue Description

Utilizing @requires on root query fields results in a broken query plan that does not return the required fields.

Link to Reproduction

Code sandbox appears broken?

Reproduction Steps

The code sandbox appears to be broken, so unable to share a working example at the moment.

As a minimum reproducible example, given subgraphs:

1:

extend schema
  @link(url: "https://specs.apollo.dev/federation/v2.5", import: ["@key"])

type Query @key(fields: "__typename") {
  b: B!
}

type B {
  id: ID!
}

and subgraph 2:

extend schema
  @link(
    url: "https://specs.apollo.dev/federation/v2.5"
    import: ["@key", "@inaccessible", "@requires", "@external"]
  )

type Query @key(fields: "__typename") {
  a: A! @requires(fields: "b {id}")
  b: B! @external
}

type A @key(fields: "id") {
  id: ID!
  a: String
}

type B @external {
  id: ID!
}

It will successfully compose. However running the following operation:

query {
  a {
    a
  }
}

Which should in theory require:

b {id}, but does not; the query plan for this results in:

QueryPlan {
  Sequence {
    Fetch(service: "2") {
      {
        a {
          a
        }
      }
    },
    Flatten(path: "") {
      Fetch(service: "1") {
        {
          ... on Query {
            b {
              id
            }
          }
        }
      },
    },
  },
}

Which basically does the inverse of what is required.

This ideally should either be A) allowed and properly handled or B) fail composition as the behavior is not supported/is broken.