Refactor: Extract common code from LaunchRequestHandler's delegate

See ILaunchDelegate.java#L25-L27

    CompletableFuture<Response> launchInTerminal(LaunchArguments launchArguments, Response response, IDebugAdapterContext context);

    CompletableFuture<Response> launchInternally(LaunchArguments launchArguments, Response response, IDebugAdapterContext context);

There is common logic in implementation for both interfaces. The main differences in implementation for debug/noDebug are:

• launchInTerminal: It constructs different command string, and then take different actions according to response.
• launchInternally: It starts debuggee process in different ways.

Refactor work should be done to make code clean and readable.

从 ILaunchDelegate.java 第 25-27 行开始，然后检查 LaunchRequestHandler 的 delegate 中 launchInTerminal 和 launchInternally 的实现。比较共享逻辑以及 issue 中描述的 debug/noDebug 差异；完成的标准是整合公共行为，同时保持 delegate 易于阅读，而不改变这些不同的启动行为。