WIP: privacy: Add USB protection entry
I talked about this in Planet GNOME. First post here https://ryuzakikk.github.io/gnome/internship-preparation/
This MR adds an entry in the privacy panel of g-c-c. From there the users will be able to check and edit their USB protection level.
We have a general on/off switch and below a drop down menu where is possible to choose when to allow/block new USB devices.
The drop down entries are: "Never", "When lock screen is active" and "Always".
USBGuard is required for this functionality to work. So we check if it is available and if it is not we gray out the drop down and the on/off switch.