Move CR UIs in the Page Index to have its own tab

I'm not exactly sure why we want to list CRs there (Simon Urli ?) but assuming we need them, I'd propose instead to contribute a new tab called "Change Requests" which would list all CRs and allow users to filter them (active, deleted, etc).

We actually don't need them here: this is the usual Change request doctab view, normally displayed along with history, information etc. It's just that CR injects that tab with a UIX and we don't have any mechanism in XS to specify that "no tab at all" should be displayed. IMO we're missing this mechanism.