Utilize a native reference popover and native reference list in the apps when switching to mobile-html.

Proposal
Add a "References" menu item for references in the existing "About this article" menu:

That when tapped, would show a native references list. RI work in mobile-html to support this is covered by T217352

Background:

Currently, the apps utilize a native presentation for the reference popover:

But include a web-based reference list in the content of the article:

With mobile-html, the reference list is being provided separately from the article content to improve article load time. It would simplify the presentation & interaction if it were all native or all web-based. In an all web-based presentation, the apps would lose the ability to gray out UX elements outside of the web view (toolbars, navbars). In an all native presentation, the reference section could be a link to a separate view similar to how the language list or edit history work currently, and the reference popovers could stay as they are currently.