Why build a new low-level container runtime?The idea of separating the low-level container runtime concerns into its own tool or microservice is not new. Outside of the Kubernetes CRI, which presents container lifecycle management as a pluggable microservice, there are simpler tools which provide a low-level container runtime as well, such as the unshare utility in util-linux, as well as another tool called Bubblewrap.But these tools are either too high-level (like the Kubernetes CRI), or they a...