[devtools] Handle i18ncube command for "cubes as packages" And add a test so that both layouts are tested. Move the test cube into a package. Related to #13001466.

etc/init.d
etc/cubicweb.d
etc/bash_completion.d
usr/bin
usr/share/doc/cubicweb-ctl
var/log/cubicweb
var/lib/cubicweb/backup
var/lib/cubicweb/instances