Add upgrades to confirmation pages

For AC, we're having to use kick-in levels for Sponsorship and Super Sponsorship, but AC attendees and staff understand these as actual badge levels. We had to hide the kick-in-level box, so this adds some functionality back in by displaying an upgrade selection that looks more like badge types.

Also factors out some of the JavaScript so it's centralized. A lot of this JavaScript is special-cased in order to get around very large tasks, so this will make it easier for us to fix it later on.
I'm leaving this block (and related code) in for now even though it's deprecated, because we don't have a firm confirmation on whether or not the Dealers Room head will want this kind of functionality.