docker-entrypoint: use natural sort for scripts to launch

entrypoint/docker-entrypoint.sh

mainline/alpine-perl/docker-entrypoint.sh

mainline/alpine/docker-entrypoint.sh

mainline/debian-perl/docker-entrypoint.sh

mainline/debian/docker-entrypoint.sh

stable/alpine-perl/docker-entrypoint.sh

stable/alpine/docker-entrypoint.sh

stable/debian-perl/docker-entrypoint.sh

stable/debian/docker-entrypoint.sh