Review app section of MR overview is not visible immediately

Propose to make the review app section of the MR overview visible as soon as it's ready, rather than after the entire pipeline completes, if possible.

In the handbook repo, the deploy pipeline stage completes. However it does not show up on the MR overview for me to browse until after the subsequent Dast stage completes. This could save several minutes. Today I develop locally to avoid these delays, which means I'm also avoiding the web IDE and other things on the on-line only workflow.

It would be useful for me to be able to browse the review app, even if Dast fails and prevents from from taking a next step like merging. The handbook is a limited use case (static site), and there may be reasons why this would be a bad idea for an application.

CC @plafoucriere @gonzoyumo @andyvolpe @leipert @samdbeckham