feat: reinstate 'high-sierra' MacOS

[Mikilio]

I confirm this feature has not been previously requested

• I have searched the issues and this feature has not previously been requested

Is your feature request related to a problem? Please describe.
With 69131b2, high-sierra has been completely removed. The reason given was that it does not support virtio devices. But as it is the last version supporting NVIDIA GPUs, the most likely desired mode of operation is passthrough anyway.

Describe the solution you'd like
I would like to know if it is possible to bring back high-sierra support.

Describe alternatives you've considered
I tried using the OSX-KVM directly, but it seems that following this guide only, I can't seem to successfully install, because networking and peripherals don't work. Quickemu solves this a lot better.

I will understand if this gets closed as not planned.