This commit moves containerd, cri-tools, docker, docker-cli and
docker-proxy from app-emulation to app-containers.
Also move app-emulation/docker-runc to app-containers as runc. The
docker-runc name seems to be an artifact from the older versions of
docker, where it needed to use a fork of runc instead of upstream. But
now, docker-runc was actually using upstream code, so simplify the
name now.
Adapt all the other files to the new package names.