Replace k8s.io endpoint

As of Kubernetes v1.33, the [corev1.Endpoints](https://pkg.go.dev/k8s.io/api/core/v1#Endpoints) API has been officially deprecated and the API server now returns warnings when reading or writing Endpoints resources. We need to migrate our codebase to use [discoveryv1.EndpointSlice](https://pkg.go.dev/k8s.io/api/discovery/v1#EndpointSlice) instead.