Refactor the launch connector design for launch and attach debugging

• For the launch debugging, we provide two kinds of implementation: SocketLaunchingConnector and ListeningConnector. Need revisit the design to see whether to keep using one kind of implementation.
• For the attach debugging, support both Socket Attach and Socket Listen. See #415

首先查看 issue 中描述的 SocketLaunchingConnector 和 ListeningConnector 实现，然后阅读 #415 以了解 attach 调试的背景。当 launch 调试确定了 connector 方案，并且 attach 调试同时支持 Socket Attach 和 Socket Listen 时，设计工作即告完成。