Add status to extension item in the extension browser

As per UX spec, items in the ExtensionManager show a status indicator in their upper right.

That could be something like "enabled/disabled", "installed" or "update available".

It needs to be defined what is shown for extension packs which can contain extensions with varying statuses.

It also needs to be defined whether the "cards" should contain interactive elements such as buttons for direct installing/updating, etc. (And how these behave in the case of packs).