Add E2E smoke test for pushing to a repository stored on a Praefect node

We need a simple test of using a repository that is stored on a Praefect node.

Such a test could have prevented this significant bug: gitlab-com/gl-infra/production#1710 (closed)

According to the documentation admin access is needed to use the repository_storage parameter, and there's no UI option to change/set it. This is no problem for Staging, but it means we won't be able to run the test on Production.

Tasks:

• Add the test and QA_CAN_TEST_PRAEFECT to enable it selectively: gitlab-org/gitlab!27295 (merged)
• Add an environment variable QA_PRAEFECT_REPOSITORY_STORAGE to the Staging project so the test can target the appropriate storage: staging!50 (merged)
• Update gitlab-qa to pass through the environment variables, to disable the test by default, and to enable it in the Praefect scenario: gitlab-org/gitlab-qa!413 (merged)
• Update nightly, canary, and production pipelines to disable the test
  • pipeline-common: pipeline-common!44 (merged)
  • nightly: https://gitlab.com/gitlab-org/quality/nightly/-/merge_requests/57