Use zstd:chunked when pushing images

[samhclark]

When publishing the images, Buildah can compress the image with zstd:chunked. Eventually, with support from bootc, this could make pulling updates a lil faster.

I ran into problems when pushing zstd:chunked images to a tag that had already been published. Not sure if that's a thing where it's hard to convert them, but I didn't mess around with it much.

The commit that reverted zstd:chunked is here
017dbc5

[samhclark]

Got a working branch on try-zstd-chunked-again (most recent commit 800cf2d). The downside is that rpm-ostree upgrade is horribly slow after this. 4 minutes, 58 seconds. (Compared to 1min,52sec gzip)

There are some existing GitHub issues about that, so maybe hold up on doing this here until that gets worked out, or it becomes the default.

There's a work tracker here containers/image#2189