CLI tool for docker-to-squashfs conversion (pure Java)

YARN-9564 defines a docker-to-squashfs image conversion tool that relies on python2, multiple libraries, squashfs-tools and root access in order to convert Docker images to squashfs images for use with the runc container runtime in YARN.

YARN-9943 was created to investigate alternatives, as the response to merging YARN-9564 has not been very positive. This proposal outlines the design for a CLI conversion tool in 100% pure Java that will work out of the box.