gateway cluster flow control

## Issue Description

Type: feature request

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

support spring cloud gateway cluster flow control

### 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?
我看sentinel支持ParamFlowRule进行集群限流，但是不支持GatewayFlowRule进行集群限流，而sentinel底层是将GatewayFlowRule转化成ParamFlowRule进行限流的。GatewayFlowRule不能集群限流时因为GatewayFlowRule没有clusterMode属性，在转化时ParamFlowRule的clusterMode属性还是默认值false。
我想给GatewayFlowRule加一个clusterMode属性，并且在GatewayFlowRule转化为ParamFlowRule时，将clusterMode属性也同步过去，来实现GatewayFlowRule的集群限流。不知道我的思路是否正确？

Start by reviewing the GatewayFlowRule and ParamFlowRule classes and the conversion path between them. Check how cluster-mode settings are represented and used for gateway flow control; done means the proposed behavior is agreed, implemented, and covered by relevant tests.

Written by the indexing model from the issue text.