Link related Koji builds for Fedora CI test jobs

[lbarcziova]

For upstream jobs, the TF jobs run using Copr builds (or independently), but for Fedora CI jobs, Koji (scratch) builds are used. Dashboard (and API) currently don't contain this information. Example: https://dashboard.packit.dev/jobs/testing-farm/928407

TODO:

• include the koji build IDs in the API result for TF similarly as we do with Copr builds IDs
• link these on the dashboard (in the TF view) conditionally