Render VIPs dynamically based on network_data.yaml

Render VIPs dynamically based on network_data.yaml

This change modifies the templates to dynamically define the VIPs
based on network_data.yaml. If a network is defined and marked
with "vip: true" in network_data.yaml, it will be included in the
overcloud.yaml which defines the deployment-level resources.

This should make it possible to create custom networks and
use them for services which use high-availability through VIPs.

Also, extraconfig/nova_metadata/krb-service-pricipals.yaml
was modified to dynamically produce the FQDN map for VIPs on
isolated networks, to match overcloud.j2.yaml.

Depends-On: If074f87494a46305c990a0ea332c7b576d3c6ed8
Depends-On: Iab8aca2f1fcaba0c8f109717a4b3068f629c9aab
Partially-implements: blueprint composable-networks
Closes-bug: 1667104
Change-Id: I71339a6ac41133e95dbc3f93abb7a9fdeb0f2da0