In the beginning, CI artifacts were resticted to ZIP files, but they
have been expanded to be JSON files, tar.gz files, and more. Prior to
this change, these gitlab-zip-metadata would be run for each of these
non-ZIP artifacts, generating lots of noise in the logs.

We now inspect the `artifact_format` query string to determine whether
to generate metadata. If the format is ZIP, which is the case for CI
archives and LSIF files, we generate metadata.

Relates to https://gitlab.com/gitlab-org/gitlab-workhorse/-/issues/272