Neutron internal dns not enabled

[Billy Olsen]

Internal instance DNS resolution does not work because the Sunbeam configuration does not configure the dns_domain_ports extension as per https://docs.openstack.org/neutron/2024.1/admin/config-dns-int.html.

This means that instances will not be able to resolve hostnames through the configuration (and other instances will not be able to resolve other instances).

In order to resolve this, the following will need to be done:

1. Add the dns_domain_ports extension to the list of extension_drivers
2. Add a configuration option for the dns_domain configuration option in the neutron charm (and the rendered neutron.conf file).
3. Add configuration options to bootstrap to allow a user to set the default dns domain for the cloud.