[feature required] Add a `Collapse All` Button in Proxies Panel and Support test latency for single node

[RulesW]

There's two feature maybe useful I met in my usage.

• A Collapse all Button in Proxies Panel. Since sometimes I have plenty of proxy-groups open, I need a button to quick close them all to find one of them. And also maybe it can add an Anchor on the right like CFW.

• Support of test latency of a single node. As I also do have of nodes, a full test sometimes cost lots of time and unnecessary. If you think these advice may useful, maybe I can create a PR as I am learning React right now. Thanks for your help.

  在使用过程中我遇见了两个需求：

  • 在 Proxies 面板添加一个收起全部代理组的功能。有时候在使用中会有很多的代理组处于打开状态，这时候我需要一个按钮快速关闭这些以找到需要的代理组。也许可以添加一个类似CFW的锚点。
  • 支持对单个节点的延迟测量。有时候有一大堆节点的时候，对全部节点进行测量是不经济也不需要的。 如果您认为这些需求有价值的话，鉴于我正在学习React，也许我可以试图提交一个PR。 感谢您的帮助。 （妈耶先写英语在写中文翻译腔味道好重

[Synchronized1]

1.我感觉可以设计在最顶端的Proxies上,一键折叠! 2.至于单个节点延迟测试的话,可以在每个节点上加上一个⚡ 奈何逻辑有....前端太水😄