Can't tell if copies in distro upload queues contain binaries or not

Querying for the contains_build property on a package_upload (queue entry) which is a copy always returns False.

This makes it impossible for queue reviewers to tell whether copies in the queue will result in binaries from the source being copied too, or if new builds will be scheduled. It is important to be able to know this if we want to be able to review copies, because we want to be able to ensure that distro builds are always done in a correct environment.

If it's convenient when fixing this, it would also be nice if the web UI also rendered the property's value too, e.g. by showing "(contains binaries)" when expanding copies, or rendering links to the artifacts like is done for non-copy queue entries.