Network Data v2 - node ports and node network config

With "Network Data v2" the goal is to move management of network resources
out of the heat stack. The schema spec [1]_ talked about the `network_data.yaml`
format and managing networks, segments and subnets. This spec follows up with
node ports for composable networks and moving the node network configuration
action to the baremetal/network configuration workflow.

Applying a network change on day 2, currently requires a full stack update
since network resources such as ports are managed by heat. It has also been
problematic to creating ports for large scale deployments, neutron on the
single node undercloud get's overwhelmed and it is difficult to throttle
port creation in Heat.