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

virtualbox-guest-utils-nox and vboxservice.service.

Provides various things—shared folders (allows accessing host's shared folders from the guest and the whole guest file system from the host), time synchronization, etc.
qemu-guest-agent and qemu-guest-agent.service.

Allows to do stuff. 🤷

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information