Add features needed by podman-machine

[cfergeau]

Before podman-machine can make use of vfkit instead of QEMU

Required:

• To avoid the need to extract kernel/initrd from disk images.
  Add EFI support #18
• A way to pass ignition config from the host to the guest
  Ignition support #35
• Serialization of the VM to disk
  Add json serialization/deserialization #46
• for easier early-boot debugging
  Add support for a GUI, virtio-input and virtio-gpu devices #44
• Usermode networking support without running gvforwarder in the guest
  Add NewFileHandleNetworkDeviceAttachment support #45

Possible improvements:

• Add Rosetta support #23

[cfergeau]

A "nice to have" feature would be the integration of gvisor-tap-vsock and vfkit to get userland networking instead of relying on the user of vfkit to setup gvisor-tap-vsock, and pass the file descriptor it wants to use to vfkit.

[cfergeau]

A "nice to have" feature would be the integration of gvisor-tap-vsock and vfkit to get userland networking instead of relying on the user of vfkit to setup gvisor-tap-vsock, and pass the file descriptor it wants to use to vfkit.

I filed #24 to track this.

[cfergeau]

podman-machine has everything it needs to use vfkit, so this can be closed.