Consider relaxing extension dependency on Microsoft C/C++

[Evan-Zhao]

This extension seems to work right out of the box with CodeLLDB configurations. (At least in my own setup) CodeLLDB supports lldb much better than the official MS C++ extension does, and I don't even have a use for the MS C++ extension now, but have to keep it because it's a required dependency of this extension.

Does it make sense to make the dependence on MS C++ optional so that users can install it on demand?