Add support for v3 Journalist Interface onion service

As of SecureDrop 1.0.0, we support v3 onion services, but the workstation/proxy currently only works with v2 addresses for connecting to the Journalist Interface. Because pilot organizations may have switched to v3-only by the time of the pilot, we need to ensure that the workstation can be configured to use a v3 Journalist Interface onion service.