configs/*: add VM guest packages and enable their services

* virtualbox-guest-utils-nox package and vboxservice.service for VirtualBox.
* qemu-guest-agent package and qemu-guest-agent.service for QEMU & libvirt.

Implements #118.
3 jobs for vm-guest in 36 minutes and 37 seconds (queued for 7 seconds)
Status Job ID Name Coverage
  Lint
passed #22208
shellcheck

00:00:22

 
  Build
passed #22209
fast-single-thread
build: [baseline]

00:14:57

passed #22210
fast-single-thread
build: [releng]

00:36:13