Adds production instance to gitlab-qa

• Adds the instance option

bundle exec ./exe/gitlab-qa   Test::Instance::Production -- --tag smoke

similar to staging for determining the version and setting the endpoint for https://gitlab.com.

• Adds support for QA_COOKIES for accessing the canary stage in production. With https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/8599 it can be set to gitlab_canary=true to direct traffic to the canary fleet.