feat: build-chunked-oci improvements

[HastD]

I can think of a few ways build-chunked-oci could be improved to make image and update sizes smaller and/or builds faster:

• Use zstd instead of gzip for layer compression. Upstream issue is container encapsulate & zstd coreos/rpm-ostree#5405. This would likely decrease both build times and image download sizes.
• Take a previous build manifest into account when rechunking the image. This is helpful to avoid packages being arranged differently into layers between successive builds, resulting in unnecessary downloading of layers that don't contain changed packages. I think fix: ensure layer annotations for build-chunked-oci are preserved #644 should solve this.
• This one is more speculative but in many cases, the base image has already been rechunked—could there be a way to essentially rechunk only the new layer added by BlueBuild while leaving the base image layers alone, rather than having to rechunk the whole image? (I'm guessing this would require more substantial upstream work though.)

Most of this depends on upstream work but I'm making an issue here to track it since BlueBuild would likely also need to make changes to take advantage of such options if they become available.