Move review-stop to the same level as start-review-app-pipeline

What does this MR do and why?

This is a simplified version of !103540 (closed)

• Construction (start-review-app-pipeline) and destruction (review-stop and review-cleanup) should be on the same level
• For the sake of allowing on_stop still works on the child pipeline, we still keep review-stop in the child pipeline, but it'll just play the one in the parent pipeline. This will not deadlock because it's just scheduling the parent one to run, and it'll not lock on the resource_group.

See #381415 (comment 1172982554)

Example jobs

• Child trigger-review-stop: https://gitlab.com/gitlab-org/gitlab/-/jobs/3720234471
• Parent review-stop: https://gitlab.com/gitlab-org/gitlab/-/jobs/3720088973