[windows]: add impeller switch to the project

On linux we updated the dart project to hold the setting as to wether impeller is enabled or not.  We need to do the same thing for windows.  It will happen here following the example of setting the thread policy:

https://github.com/flutter/flutter/blob/66aaa9adb000b3ebec5531933b4461467cb394e9/engine/src/flutter/shell/platform/windows/client_wrapper/include/flutter/dart_project.h#L120