SCALE: Add feature to import/export VMs in OVA format

I've created a post on the forum with suggestions to improve the UX/UI for user focused on Virtualization:

https://www.truenas.com/community/threads/are-these-virtualization-features-on-the-roadmap.90063/

I'll split the suggestions on multiple tickets focused on specific features.

(6) Import/Export VMs in OVA format

Some developers use the OVA format to distribute appliances and demos of their applications (e.g. OpenNebula and HomeKit). It's also a versatile format to transfer VMs between systems and different hypervisors.