Support renaming `@link`

[martinbonnin]

Support this:

extend schema
  @magic(url: “https://specs.apollo.dev/link/v1.0”, as: “magic”)
  @magic(url: “https://specs.apollo.dev/federation/v2.0”, as: “fed2”)
type Product @fed2__key(fields: "id") {
  id: ID! 
}