token server部署alone模式，dashbord控制台集群流控配置后，重启client配置被清空了

## Issue Description

1、dashbord控制台集群流控配置的目的是什么，仅仅是为了动态修改并更新吗，因为我client启动已经assign token server了，这里还需要做关联配置吗？

//硬编码方式连token server
ClusterClientAssignConfig clientAssignConfig = new ClusterClientAssignConfig(tokenServerHost,tokenServerPort);
ClusterClientConfigManager.applyNewAssignConfig(clientAssignConfig);
SentinelProperty property = new DynamicSentinelProperty(clientAssignConfig);
ClusterClientConfigManager.registerServerAssignProperty(property);

2、token server部署alone模式，dashbord控制台集群流控配置后，重启client配置被清空了。这里比较疑惑，集群流控配置当前应该默认是没有持久化的，请问下具体怎么实现集群流控持久化呢？

### Describe what happened (or what feature you want)

### Describe what you expected to happen

### How to reproduce it (as minimally and precisely as possible)

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### Tell us your environment

### Anything else we need to know?

Start with ClusterClientAssignConfig, ClusterClientConfigManager, and DynamicSentinelProperty, then trace the standalone token-server and dashboard configuration flow. Reproduce the dashboard cluster-flow configuration, restart the client, and compare the configuration before and after restart. Done should establish whether persistence is supported and identify the required behavior or documentation.

Written by the indexing model from the issue text.