WIP: OXUI-878: Onboarding wizard supports upsell

Implementation notes

With the new onboarding wizard, upsell was not implemented at first. This MR implements the upsell functionality known from the previous wizard back again and also adds an e2e-test using the demo mode to test for it.

Please describe your changes/bugfixes with some words to help the reviewer understand what you want to do

• add upsell back into onboarding wizard, for now the only visual indication is a different .svg icon (fa-lock) where the right arrow is for non-upsell apps
• adds an e2e tests which uses the demo mode to check if normal apps are connectable whilst upsell-apps (e.g. Exchange Active Sync) opens the upsell modal dialog. there's no visual check for the visual indication yet

Questions/TODO:

1. The MW sends missing_capabilities with the config, which previously was used to determine if an app was "Premium". I haven't tested for that case yet and have opted out to use the apps and capabilities only for now. (since they were testable with demo-mode)
2. Is a different .svg lock enough for the differentiation between (non-)premium apps or should the visual indication be more visible? If so, how?