Modify generic role template to support custom networks

Modify generic role template to support custom networks

Render all per-network resources and interfaces via j2 to enable
future support for custom networks via network_data.yaml

Note this doesn't enable custom networks for the built-in roles
as we skip j2 rendering for them, this will be resolved by converting
them to use the generic role template instead of the hard-coded
ones listed in the j2_excludes.yaml.

Depends-On: I18fa3829ff38ac200550d8e36bbe334c0005da22
Change-Id: I49565f9389f3ec9aef4861e23a3bed64a85501e6
Partially-Implements: blueprint composable-networks