Unfortunately, the change of "depot: remove empty config from
pkg/nano3d" broke the manual deployment of the nano3d demo because no
<config> is provided in this case.
This patch splits pkg/nano3d into two variants. The regular nano3d pkg
comes with an empty <config/> node as before. The unconfigured_nano3d
pkg does not feature any <config/> node and can thereby be configured
via a ROM route to a dynamic-rom service.
