encode all resources; use concrete value for network

This makes it easier to serialize/deserialize a container's resources in full,
including the rich Network object. Network pools now strictly deal with
*network.Network types, which makes things a lot easier. Didn't really need
that intermediate interface.

At this point a recovered container can have its information retrieved, as all
of its resources are now restored. (They are not yet removed from the pool,
though.)

[#61232150]