T7638: image-sdk: Generate VirtualBox OVA appliance image
https://phabricator.apertis.org/T7638
Current SDK images requests to manually setup the Virtual Machine in VirtualBox, as we're only provinding the disk image (.vdi file).
This commit adds support to generate a VirtualBox Appliance image (.ova file) that works out of the box.
OVA files are tar archives which include the disk images (currently generated .vdi file) plus metadata describing the parameters of the virtual machine in OVF format (an XML file).