Configuring authorization policies (GCPAuthzPolicy) on Cloud Service Mesh

## Feature Feature Configuring authorization policies (`GCPAuthzPolicy`) on Cloud Service Mesh sidecars on Google Kubernetes Engine (GKE) is now available ([Preview](https://cloud.google.com/products#product-launch-stages)). This feature is supported only for Cloud Service Mesh with the Gateway API. You can allow or deny inbound HTTP requests at the namespace or workload level, or delegate decisions to an external authorization engine (`GCPAuthzExtension`). For more information, see[Setup authorization policies on sidecars on GKE](https://cloud.google.com/service-mesh/docs/gateway/authorization-policy-sidecar).