Move the CNG triggering to a dedicated job in the `test` stage.
This is to save between 5 and 16 minutes upon retries of the review-deploy
job, see https://gitlab.com/gitlab-org/gitlab-ce/issues/56538#note_133412287.
This is to save between 5 and 16 minutes upon retries of the review-deploy
job, see https://gitlab.com/gitlab-org/gitlab-ce/issues/56538#note_133412287.