macOS virtualization executor

Description

Since macOS 12, Apple Silicon VMs can (only) be run using Apple's own virtualization framework which is part of the operating system. As far as I know, Parallels and VMware make use of this framework when a VM for Apple Silicon is being created (that's why Snapshots can not be created etc.).

Proposal

Add an executor which uses the virtualization framework "directly". Since the parallels and virtualbox executors use a separate commandline tool for starting/stopping VMs and Apple does not provide one, it looks like https://github.com/cirruslabs/tart did that job already.