Windows 10 Version 2004 - September 2021 Samples Update

* Json: Add deletion support, improve error handling
* Printing: Force printDocument to null to ensure it is not kept alive by
  the XAML navigation cache (not a problem in this sample since it doesn't
  enable the navigation cache, but fixed for completeness)
* New C++/WinRT samples: AppServices, Json
* Archived C++/CX samples: AppServices