Fix url for object store artifacts

What does this MR do?

There's a problem in how we pass connection configuration and how it is being evaluated by Fog when requesting URL. The problem of mocking the data.

It was not caught by tests as we used Hash, instead of Settingslogic. Settingslogic has the strange behavior where it expects to hold string keys in order to resolve them, as symbol keys don't work properly.

This makes sure that all Settingslogic keys are strings, and we also do the same for our tests.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/3172