Include "changed pages" widget in visual review function

With https://gitlab.com/gitlab-org/gitlab-ce/issues/53390 we provided the ability for users to manually review the visual and application changes within a review app. As a follow up to that, we should port the "which pages have changed" widget from the Merge Request into the Visual Review function. This widget is already smart about what it knows about the MR and the changes, and thus that logic will be the same in the Visual Review function.

That way, I can quickly navigate to only / all of the parts of the application that have changed.