Build live ISO using osbuild

[jlebon]

This adds a new osbuild pipeline for building the live ISO using the new
org.osbuild.coreos.live-iso mega stage.

Still missing is changing cmd-buildextend-live to call osbuild
instead. I think we'll need to ratchet this in using e.g. an env var
like we did for the other osbuild artifacts. E.g. COSA_OSBUILD_LIVE
would control whether to use the old logic or the new one. And then turn
it on in rawhide, etc...

The new cmd-buildextend-live would also take care of extracting the
live artifacts from the live ISO to insert into meta.json.

[openshift-ci]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[jlebon]

Requires: osbuild/osbuild#1842
Requires: osbuild/osbuild#1843
Requires: osbuild/osbuild#1844
Requires: #3846
Requires: coreos/coreos-installer#1511

[jlebon]

This works locally! To test it:

$ cat runvm-osbuild-iso-config.json
{
  "osname": "fedora-coreos",
  "ostree-ref": "40.20240627.dev.0",
  "ostree-repo": "/srv/fcos/tmp/repo",
  "ostree-container": "/srv/fcos/fcos-with-newer-coreos-installer.ociarchive",
  "metal-filename": "/srv/fcos/builds/40.20240812.dev.0/x86_64/fedora-coreos-40.20240812.dev.0-metal.x86_64.raw",
  "metal4k-filename": "/srv/fcos/builds/40.20240812.dev.0/x86_64/fedora-coreos-40.20240812.dev.0-metal4k.x86_64.raw",
  "container-imgref": "",
  "extra-kargs-string": "mitigations=auto,nosmt",
  "image-type": "live-iso",
  "cloud-image-size": "10240",
  "metal-image-size": "2405",
  "squashfs-compression": "lz4",
  "rootfs-size": 0,
  "live-efiboot-img-size": 16
}
$ cosa supermin-run --cache /usr/lib/coreos-assembler/runvm-osbuild --config runvm-osbuild-iso-config.json --mpp /usr/lib/coreos-assembler/osbuild-manifests/coreos.osbuild.x86_64.mpp.yaml --filepath out.iso
...

And we get an out.iso! Though it doesn't fully work yet. It boots fine (tested both BIOS and UEFI), but we're not switching root yet. Also only tested on x86_64 for now.

[openshift-merge-robot]

PR needs rebase.

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[ravanelli]

Tested, lgtm! Thanks for working on it @jlebon!

[ravanelli]

I also started working on: #3861 i