1. Renames review to review-deploy.
2. Renames stop_review to review-stop.
3. Adds a build-qa-image job to the prepare stage and save the QA
  Docker image as artifact (example:
  https://gitlab.com/gitlab-org/gitlab-ce/-/jobs/120967019).
4. Adds a manual review-qa job to the test stage to run QA tests
  against the Review App (example:
  https://gitlab.com/gitlab-org/gitlab-ce/-/jobs/120967238).
5. Make the review-deploy job plays the review-qa job as soon as the
  Review App is deployed (example:
  https://gitlab.com/gitlab-org/gitlab-ce/-/jobs/120988775).
6. Updates the Review Apps documentation accordingly.
Signed-off-by: Rémy Coutable <remy@rymai.me>