Make standalone container registry tests simpler to run
As part of a [project horse work](https://gitlab.com/gitlab-com/gl-infra/gitlab-dedicated/team/-/issues/90) item, we were looking to automatically test Container Registry after provisioning. These tests were added in https://gitlab.com/gitlab-org/quality/testcases/-/issues/1052 , and it is known that it is a bit more complicated to run the end-to-end tests for Container registry with QA due to needing operational Runner setup.
## Problem description
Apart from a known runner requirement, the QA tests for container registry have other limitations. They can either run if:
1. Use an option to run from scratch against an omnibus instance. By invoking https://gitlab.com/gitlab-org/gitlab/-/blob/master/qa/qa/specs/features/browser_ui/5_package/container_registry_omnibus_spec.rb , registry is enabled, runner setup and the tests executed
1. Run against an already setup environment https://gitlab.com/gitlab-org/gitlab/-/blob/443d12193c241fe2de017fdbb81ba377ed8ac552/qa/qa/specs/features/browser_ui/5_package/container_registry_spec.rb#L5
If we select the option of running against a setup environment, the tests only run against staging and pre for gitlab.com environments.
Even when `only: { subdomain: %i[staging pre]` restriction is removed by editing the code, running the Registry only test is a bit confusing:
```
bundle exec bin/qa Test::Instance::All https://INSTANCE -- qa/specs/features/browser_ui/5_package/container_registry_spec.rb --tag reliable
```
## Proposal
This issue is proposing to make an assumption that if a Runner is setup and enabled on any running instance, we are able to run a QA e2e test on any domain.
Ideally, I'd like us to be able to run all Container registry tests by supplying a tag, eg.:
```
gitlab-qa Test::Instance::Any VERSION https://example.com --tag orchestrated --tag registry
```
issue