bump k8s.io/kube-openapi to v0.0.0-20260502001324-b7f5293f4787

Updates k8s.io/kube-openapi across all staging modules and vendors the new
revision. Key changes upstream:

- builder/openapi.go, builder3/openapi.go: use common.EscapeJsonPointer()
  when keying definition names into swagger.Definitions / spec.Components.Schemas,
  fixing incorrect lookups for types whose names contain JSON-Pointer-reserved
  characters (e.g. '/', '~').

- pkg/generators/apidefinitions/loader.go (new): LoadAPIVersion() reads an
  apiversion.yaml from a source-tree directory and validates its TypeMeta,
  providing a declarative way to describe API versions in-tree.

- pkg/generators/apidefinitions/types.go (new): APIVersion type that carries
  the schemeGroupVersion / kindAPIVersion metadata consumed by the loader.

- pkg/generators/config.go, openapi.go, model_names.go: minor generator
  improvements accompanying the apidefinitions loader addition.

- pkg/generators/rules/list_type_streaming_tags.go: streaming-tag rule fix.

- pkg/schemaconv/openapi.go, proto_models.go: schema conversion cleanups.

- pkg/validation/validate/result.go: validation result cleanup.

Previous version: v0.0.0-20260317180543-43fb72c5454a
New version:      v0.0.0-20260502001324-b7f5293f4787

Kubernetes-commit: eaf347cecb168ee85fc77ffc9a5cda4eb99ce1ca