Don't apply queryTransforms to the first level

[stubailo]

If we have an addTypename transform, we want this:

{
  myRootField {
    stuff
  }
}

To become this:

{
  myRootField {
    __typename
    stuff
  }
}

And not this:

{
  __typename
  myRootField {
    __typename
    stuff
  }
}

So we don't want to add fields to the root mutation or root query selection set on operation definitions.

[Poincare]

Done with #463