Webservice: Default to IPv6 compatible binds

What does this MR do?

Webservice: Default to IPv6 compatible binds

We disabled IPv6 compatible binds in !4382 (merged) because of a issue with throttling of unauthenticated web traffic.

Now with gitlab-org/gitlab!196981 (merged) rails should see the real client IP, even if the client or one of the intermediate proxies was mapped to an IPv6 address, so we can default to IPv6 compatible binds.

Uses null listeners instead of * to help with gitlab-org/caproni#109.

Changelog: changed

Closes #6084 (closed)

Related issues

Closes Webservice: Enabling IPv6 breaks unauthenticate... (#6084 - closed) • Clemens Beck

Relates caproni: monolith-edit-mode setup.sh hack — WEB... (gitlab-org/caproni#109) • Manuel Schönlaub

Test instructions

To test the behavior with kind, create a dual and a ipv6 cluster and confirm the instance comes up healthy:

# kind config yaml
kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
networking:
  ipFamily: dual
  # ipFamily: ipv6
  # ipFamily: ipv4
nodes:
- role: control-plane
  extraPortMappings: []

Notes:

• If you are using CloudNative PG and your Cluster is not coming up healthy, make sure to use a version not impacted by https://github.com/cloudnative-pg/cloudnative-pg/issues/10679.
• If you are using Envoy Gateway you might need a custom spec.ipFamily=IPv6|Dual in your EnvoyProxy.

Author checklist

For general guidance, please follow our Contributing guide.

Required

For anything in this list which will not be completed, please provide a reason in the MR discussion.

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• Tests added/updated.
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  • Describe how you did it in a comment.
    • See test instructions above.
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