Add debugger pseudo-variable to display "returned" value like C# debugger provides

I'm not sure if this is possible or not but it sure would be nice to have. Many times PowerShellers just let various statements "output" from the function so after you've called a function (and you don't capture the output in a variable) it is hard to tell what output the called function is contributing to the output of the current function/script.

首先调查 PowerShell 调试器支持，以及调试器值如何暴露给编辑器。确定为函数返回的输出提供伪变量是否可行，并在确定实现和测试入口点之前定义预期行为。完成标准是该功能在调试期间能够一致地工作，并且有涵盖代表性函数输出的测试。