feat: add boot-uki.sh script to run UKI build in QEMU

boot a locally build garden linux with qemu using EFI/OVMF boot and
ignition for firstboot provisioning. The script targets macOS for now.
The following tools are required:

* qemu (for QEMU and OVMF firmware)
* podman (for running a local OCI registry)
* oras (for pushing the UKI as an OCI artifact to the local registry)
* hdiutil (for creating the ignition config-drive ISO)
* python3 (for merging ignition config and patching UKI cmdline)
* patch in console ttyS0
* use dbgimage
* bash >4 (for the main script)

To login after provision one can use the admin/admin user created by the
script, e.g. with `ssh -p 2222 admin@localhost` if --ssh is used or
directly using the console.

Author: toanju