Remove "Browse all fonts" tab and move each provider tab up a level

I think this will be a good first step for #1544156: [META] Simplify/reduce which functionality is available on which screens. The "Browse all fonts" link is already a non-page that redirects to the first available provider, so this wouldn't be removing an actual page. It would remove a step in getting to a particular provider list, and also open up the third level of tabs for switching between browse, configuration, and import for the selected provider.