NetworkSetup: simplify UI layout

* Temporarily disable the non-working Profiles popup
* Remove the currently single-tabbed TabView
* Remove duplicate apply and revert buttons in the interfaces add-on.

The goal here is to remove functionalities not available in the current
network preferences, and finish the other parts, so we can put this new
preferences panel in service now. We can re-add the extra functionality
later.
NetworkSetup: list and join wireless networks

* Reuse the logic from the old network preflet for now. Something better
can be done later.