We need to use Garasign (and @mongodb-js/signing-utils) to sign linux tarballs for mongosh.

• https://github.com/mongodb-js/mongosh/pull/1769 is a WIP branch that signs a dummy file successfully with the new signing tools.
• Garasign credentials are already a part of the mongosh evergreen project
• Depending on the outcome of MONGOSH-1685, we may be moving the signing logic into the packaging phase instead of the release phase.
• A list of all currently gpg signed artifacts can be found on existing mongosh github releases (ex: https://github.com/mongodb-js/mongosh/releases/tag/v2.1.1)