In NetworkManager, there is a global "wwanEnabled" setting. We do not typically deal with this because toggling it off shuts off cellular in ModemManager (the mobile data toggle just disconnects the connection instead).
Here we ensure that we address the case when "wwanEnabled" is off, and ensure that it's on when mobile data is toggled on. Also remove a check in the SIM page that seemed to depend on it.
Having the KCMs that are mobile specific here makes more sense than in the settings application. Historically plasma-settings had a faster release cycle than Plasma, but the application is now moving to the Plasma release schedule and so it makes sense do this now.
