builtin/k8s: Introduce Ingress resource support for Kubernetes Releaser

.changelog/2261.txt

@@ -0,0 +1,4 @@
+```release-note:improvement
+plugin/k8s: Add new ability to release by creating an ingress resource to route
+traffic to a service backend from an ingress controller.
+```

builtin/k8s/plugin.proto

@@ -27,6 +27,9 @@ message Resource {
   message Service {
     string name = 1;
   }
+  message Ingress {
+    string name = 1;
+  }
 }
 
 // This represents the state of the TaskLaunch implementation.