Support using [ReferenceResolver] when using resolver types with schema first.

Is your feature request related to a problem?

AFAIK, the only option to integrate schema first with Apollo Federation (specifically entity resolution) is to add a type extension that completely overwrites the the key/field and specifies the reference resolver. This seems to go against the idea of doing schema first as extensions seem to occur after the schema is bound. (Unsure if overwriting types with extensions during schema first is really supported)

The solution you'd like

I'd like to be able to use AddResolver<TResolver> and be able to decorate a method on the TResolver class with the [ReferenceResolver] attribute.

Full example:

// Configuration
builder.AddDocumentFromFile("./schema.graphql")
  .BindRunetimeType<UserDto>("User")
  .AddResolver<UserResolver>("User");

// UserResolver
public class UserResolver
{
  [ReferenceResolver]
  public Task<UserDto?> ReferenceResolver(int id)
  {
    return new UserDto(id);
  }
}

public record UserDto(string Id);

# schema.graphql
extend schema
  @link(url: "https://specs.apollo.dev/federation/v2.0",
        import: ["@key"])

type User @key(fields: "id") {
  id: ID!
}

Stretch goal, if we could get a schema first example under the Apollo Federation project.

Product

Hot Chocolate

Start by tracing schema-first binding through AddDocumentFromFile, BindRunetimeType, and AddResolver, then inspect how [ReferenceResolver] methods are discovered. Done means the provided UserResolver and schema-first Apollo Federation example work without a type extension, with coverage for the demonstrated configuration.