generating from CRD supports kubernetes 1.23 feature: validation rules

[amyXia1994]

Enhancement

Since k8s v1.23, the validation rules are introduced to use CEL for expressing validation rules. This feature is to enhance the structrual schema validation in CRD via the vendor extension x-kubernetes-validations

kcl openapi needs to support this feature:

1. augment the KCL OpenAPI spec
2. support generate corresponding code

ref: https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions/#validation-rules