v1 network render to netplan does not render IPv6 global nameserver address

This bug was originally filed in Launchpad as [LP: #1980877](https://bugs.launchpad.net/cloud-init/+bug/1980877)

Launchpad details

affected_projects = []

assignee = None

assignee_name = None

date_closed = None

date_created = 2022-07-06T20:46:34.682710+00:00

date_fix_committed = None

date_fix_released = None

id = 1980877

importance = low

is_complete = False

lp_url = https://bugs.launchpad.net/cloud-init/+bug/1980877

milestone = None

owner = chad.smith

owner_name = Chad Smith

private = False

status = triaged

submitter = chad.smith

submitter_name = Chad Smith

tags = []

duplicates = []

_Launchpad user **Chad Smith(chad.smith)** wrote on 2022-07-06T20:46:34.682710+00:00_

cloud-init v 22.2:

Example config with subnet `type: ipv6_slaac` doesn't render any nameserver information in config /etc/netplan/50-cloud-init.yaml when global nameserver is provided.

Steps to reproduce:

cat > network-config <