Add ubuntu drivers backend

[leolost2605]

Fixes #140

Should now be on par with what appcenter does. The only open question for me is this:

• Do we still need to install kernel headers like it's currently done in appcenter? I've recently seen a PR about adding them by default so I don't know?

[danirabbit]

@leolost2605 Yeah we've had people, especially with the nvidia driver, who want to switch to another version of the driver. It looks like Ubuntu lists them all as radios: https://linuxconfig.org/wp-content/uploads/2019/12/02-how-to-install-the-nvidia-drivers-on-ubuntu-20-04-focal-fossa-linux.png

[leolost2605]

Ok I finally got around to testing this at least with nvidia drivers and it should work now.

Some things to note:

• You currently can't remove drivers because that would require running autoremove and since it's currently the same in appcenter this is left to follow up PRs
• With nvidia drivers, installing another one while one is already installed automatically removes the other one. They aren't shown with radio buttons because that would require either assuming all drivers with nvidia in their name are for the same device or redoing quite a lot of this and I kind of don't want to do either since I don't have a lot of time ATM. Also it is on par with appcenter and I would say even a bit more understandable for the user.
• Add driver view switchboard-plug-about#300 is the corresponding UI PR

[leolost2605]

See #141 for v2 of this