Add support for running ScyllaClusters on IPv6

[tnozicka]

Is this a bug report or feature request?

• Feature Request

What should the feature do: Allow exposing ScyllaClusters on IPv6 and add a testing coverage.

What is use case behind this feature: UX, scalability.

Additional Information: From the top of my head I assume this requires us:

• to move away from ClusterIPs to PodIPs
• tweak a few places like the code that serves probes
• setup a CI with Kubernetes cluster on IPv6