Add info object type

[vardhanapoorv]

This PR adds support for passing info object and fixes the error code returned for webhook.

Example -

async function authorsByName({ args, dql, info }) {
    const results = await dql.query(
        `query queryAuthor($name: string, $numLikes: int) {
              queryAuthor(func: type(Author)) @filter(eq(Author.name, $name)) {
                  name: Author.name
                  dob: Author.dob
                  reputation: Author.reputation
                  posts: Author.posts @filter(eq(Post.numLikes,$numLikes)) { 
                     title: Post.title
                  }
              }
    }`,
        {
            $name: args.name,
            $numLikes: info.field.selectionSet[3].arguments.filter.numLikes.eq,
        },
    );
    return results.data.queryAuthor;
}

Use-case: https://discuss.dgraph.io/t/13179
Related Dgraph PR: hypermodeinc/dgraph#7718

[abhimanyusinghgaur]

LGTM, CI seems to have some issues.