[validation-gen] ValidateUpdate Support [LARGE CHANGE]

[aaron-prindle]

What would you like to be added?

Issue tracks adding ValidateUpdate support which is required for any k8s API that needs to validate changes during updates. ValidateUpdate refers to validation that runs on each update to a k8s API object.

Estimated Tasks:

• Design and implement plumbing for oldObject through all validation calls
• Define patterns for authoring update validators
• Determine when update validators should trigger (building on CEL transition rules experience)
• Add tests for update validation paths

Why is this needed?

ValidateUpdate is required for k8s APIs that needs to validate changes during updates. This is fundamental to Kubernetes API validation patterns and as is a requirement to fully implement declarative validation