Allow toggling access logs for API tests

Problem

While working on !49 (closed), we found the API tests output to be heavily polluted by the HTTP server access logs. Example: https://gitlab.com/gitlab-org/container-registry/-/jobs/466455530#L568 (starting at line 568).

These logs make it much harder to spot benchmark results and specific application log messages.

Solution

We should provide a way to toggle the access logs during the API tests and disable them by default. Result: https://gitlab.com/gitlab-org/container-registry/-/jobs/467544717#L568 (starting at line 568).