Tracker for switching to chunked ostree container images

[cgwalters]

ostreedev/ostree-rs-ext#69 has been shipped in the ostree stack for quite a while. However, us actually making use of it turned out to block on dealing with how we inject GPG signatures, which was fixed in ostreedev/ostree-rs-ext#301

But that isn't in an rpm-ostree release yet, so I made registry.ci.openshift.org/coreos/coreos-assembler:continuous which has rpm-ostree from git.

Then we just landed coreos/coreos-assembler#2902 in coreos-assembler, so along with coreos/fedora-coreos-config#1698 for rawhide, I manually kicked off a force build job: https://jenkins-fedora-coreos-pipeline.apps.ocp.fedoraproject.org/job/build/746/console

After this:

• Some sanity checking that e.g. existing FCOS stable can rpm-ostree rebase --experimental ostree-remote-registry:fedora:quay.io/coreos-assembler/fcos:rawhide
• Verify that podman builds work with it
• Get rpm-ostree released with this fix
• Wait until coreos-assembler picks it up
• Update the code changed by coreos/coreos-assembler@de628bc to hard require the new API
• Switch all FCOS streams to oci-chunked
• Profit

[cgwalters]

Update: https://jenkins-fedora-coreos-pipeline.apps.ocp.fedoraproject.org/job/build/751/console succeeded!

quay.io/coreos-assembler/fcos:rawhide is now a chunked image.

[cgwalters]

OK this now blocks on ostreedev/ostree-rs-ext#309

[cgwalters]

This is done!