ClusterFlowConfig的id为Long类型导致灵活性较差

## Issue Description
企业自建dashboard支持对批量组资源的限流，dashboard下发流控规则时会下发rule与group，要求属于该group下的资源都被流控，在SDK侧则需要根据group id得到分组下的所有资源，进而生成一个集群内相同的ClusterFlowConfig id。
原本的clusterId的生成思路很简单，使用“ rule id +资源id ”即可，但拼接后的结果会导致long溢出。

期望：或许该id使用String更为合适，灵活性更高

Start by tracing ClusterFlowConfig and the SDK path that derives its id from the rule id and resource or group id. Check how the id is exchanged between the dashboard and SDK, then identify the affected usages and tests. Done means group-based flow-control rules can use the generated id without Long overflow and remain consistent across the cluster.

Written by the indexing model from the issue text.