Add option to clone VM by default on run, and prompt for restore on end

This is an idea that's based on some Discord chatter; some people are already working on bits of this, but it gave me the idea for a unified interface:

Provide an option for APFS-level cloning of the VM when you run it, with the option when you close the VM to accept changes from that session or revert to previous version. Sort of like using -snapshot in QEMU, but this will work for Apple VM as well, will be faster, and will provide a single solution no matter the VM configuration/back end.

This is directly related to issue #2688