Ensure oldest supported Kubernetes version is using webhooks for nightly conformance tests

[mpstefan]

As a user of NGF
I want NGF to ensure webhook validation is enabled for earlier versions of Kubernetes when testing conformance
So that conformance is properly tested on the earlier version of Kubernetes my environment is using.

Acceptance

• Automated conformance testing enables webhook validation on the earliest support version of Kubernetes.
• In pipeline and local test runs