feat: use stub object storage in tests

What does this MR do?

This MR adds an object storage to the gitlab server stub and replace usage of local zip file with links to the object storage. This is closer to a production environment and should allow better profiling/testing locally.

This is a Draft and it will likely be split into several MRs (adding object storage support also uncovered a few bugs).

TODO

• I added the Changelog trailer (e.g. Changelog: added) to the commits that need to be included in the changelog
• I added unit tests or they are not required
• I added acceptance tests or they are not required
• I added documentation (or it's not required)
• I followed code review guidelines
• I followed Go Style guidelines