Re-write wwan plugin
This uses cc-wwan-device.c copied from gnome-control-center without any modification.
The following features/fixes are also implemented:
- Handle multiple devices
- Handle PUK unlocking
- Close prompt if the device got removed
- Fix showing the wrong unlock count
Please note that only around 30% of cc-wwan-device.c is used. I used the file as such so that it will be easy to update on changes.