XPS and PDF file printing samples

• XpsFilePrint: a project (AOT friendly) that demonstrates how to print an XPS file (to any printer, including XPS, PDF, ...)
• PdfFilePrint: a project (AOT friendly) that demonstrates how to print a PDF file (to any printer, including XPS, PDF, ...)
• CustomPrintDocument: a WinUI3 project (which is not AOT-friendly) that implements a custom WinRT IPrintDocumentSource, usable without any XAML, GDI, WPF or Reach Framework. It supports printing XPS or PDF files (including preview). For PDF, it implements two printing mode: one based on XPS and another based on Direct2D which outputs higher quality PDF prints.