Use VyOS python libraries more

[p3lim]

Currently we elevate vbash to run commands and check for container images, we could talk to the VyOS libraries directly instead, probably saving a bunch of time and makes it possible to accurately handle exceptions.

https://docs.vyos.io/en/latest/contributing/development.html#python

[p3lim]

After looking a bit more at it, it'd severely hamper #6 as vyaml would only be able to run on actual VyOS. From the quick research I did I found the VyOS python libraries are not complete from source, and depend on system-level data to run.