Fixup #2970: Add Missing Label app.kubernetes.io/part-of: ingress-nginx

-    Add missing label `app.kubernetes.io/part-of: ingress-nginx` for deploy example
-    Update new labels for docs/deploy and docs/examples
-    Update new labels for test/e2e and test/manifests
-    Update new labels for images/nginx

Also close #3001

build/dev-env.sh

@@ -52,5 +52,5 @@ echo "updating image..."
 kubectl set image \
     deployments \
     --namespace ingress-nginx \
-    --selector app=ingress-nginx \
+    --selector app.kubernetes.io/name=ingress-nginx \
     nginx-ingress-controller=${DEV_IMAGE}