Option to run in recovery mode

[fkorotkov]

Fixes #25

@trodemaster pointed out that @saagarjha found out the private API to start a VM in recovery mode. I kindly looked at VirtualApple implementation.

[fkorotkov]

The only problem that VirtualApple doesn't have a LICENCE file and I'm not sure if we can use it as a reference. @saagarjha, could you please clarify if it's OK by you that we used your finding. I've added a comment in VM+Recovery.swift to reflect our appreciation.

[saagarjha]

I went ahead and licensed VirtualApple under GPLv3, so you are free to use it under the terms of that license.

As a side note, I'm not a lawyer but I don't think I could claim copyright on the technique of booting into recovery, since it's morally just one line of code and unlikely to be considered large enough to be a work by itself. This isn't quite relevant here since you are using my specific way of calling that SPI, but had you done it yourself it probably would've been fine. Credit is always nice, though, regardless of whether it's required :)

As another side note, you may wish to look into using MainActor to execute your calls ;)

[fkorotkov]

@saagarjha thank you for your response! Reworked the invocation method in f2de926. Kudos for finding out about the _VZVirtualMachineStartOptions! 🙌

[dan-snelson]

Confirmed working in 0.5.0:

tart run 12.4_21F79-base-clone-2022-05-20-164841 --recovery