feat: external managed cluster registration and node handling

Hello fellas,

Since cloudstack kubernetes provider is successor of cloudstack cloud controller, shouldn't it also allow to register external managed clusters automatically? I am not saying it should be mandatory, but would be great if we had a choice. So it would fetch information about nodes and register cluster to the cloudstack, besides that it could handle node removal if virtual machine is removed and so on.

该 issue 未指定任何文件、测试或入口点。首先明确外部集群注册和节点移除的预期行为，然后定位 provider 现有的集群和节点处理路径。完成内容应包括已达成共识的范围、实现，以及涵盖注册和移除的测试。

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