[VK] Use Cache controller and Make create/delete pod Concurrently (#373)

* Add k8s.io/client-go/tools/cache package

* Add cache controller

* Add pod creator and terminator

* Pod Synchronizer

* Clean up

* Add back reconcile

* Remove unnecessary space in log

* Incorprate feedbacks

* dep ensure

* Fix the syntax error

* Fix the merge errors

* Minor Refactor

* Set status

* Pass context together with the pod to the pod channel

* Change to use flag to specify the number of pod sync workers

* Remove the unused const

* Use Stable PROD Region WestUS in Test

EastUS2EUAP is not reliable

vendor/k8s.io/client-go/tools/cache/doc.go

@@ -0,0 +1,24 @@
+/*
+Copyright 2014 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package cache is a client-side caching mechanism. It is useful for
+// reducing the number of server calls you'd otherwise need to make.
+// Reflector watches a server and updates a Store. Two stores are provided;
+// one that simply caches objects (for example, to allow a scheduler to
+// list currently available nodes), and one that additionally acts as
+// a FIFO queue (for example, to allow a scheduler to process incoming
+// pods).
+package cache // import "k8s.io/client-go/tools/cache"