Building 'chunked' images to minimize download size on update

[kkaempf]

After #1512 is done, we should run an experiment with chunked builds and podman.

container-compression-format:FORMAT
"Sets a compression format for container layers. Possible values are gzip, zstd, zstd:chunked. Every value other than gzip is only supported by podman and buildah."

The zstd:chunked option should allow for dramatically reduced download sizes when updating containers. Reportedly podman then compares layers on a file-by-file basis and only downloads changed files. This should be even more efficient than delta rpms.

[kkaempf]

See #1444