Allow running full QA suite against the GitLab image that's currently deployed on staging (including the orchestrated scenarios)

This is a prerequisite to completing https://gitlab.com/gitlab-org/quality/team-tasks/issues/217

This MR does all necessary changes required to run a full QA suite, including the orchestrated scenarios against the same revision as deployed on staging.

The most important change in this MR is allowing GitLab::QA::Release to receive a separate QA release image.

With these changes, the tests would run against the release provided by RELEASE env variable if USE_STAGING_REVISION_QA_IMAGE is also set by using the QA image for the deployed staging version.

Once merged, the next step would be to trigger this pipeline from the infra deployer pipeline such as https://ops.gitlab.net/gitlab-com/gl-infra/deployer/pipelines/84521