Without this change, the Route53 plugin is listed twice when running
Certbot interactively (once under the old name, once under the new name).
This change ensures only the new name is shown, while maintaining hidden
backwards compatibility with the old name.
This change renames certbot-route53 to certbot-dns-route53 and updates
the package's setup.py file to maintain backwards compatibility.
Testing Done:
* Run `certbot` with `-a certbot-route53:auth`, verify the plugin runs.
* Run `certbot` with `--dns-route53`, verify the plugin runs.
