* print: xps_driver says whether a Windows printer's driver renders XPS itself
craft_print::xps_driver(printer) reads PRINTER_DRIVER_XPS through winprint's new
PrinterDevice::is_xps_driver (storytold/winprint.rs#21): Some(true) for v4 drivers and v3
drivers with an XPS rendering filter, Some(false) for GDI drivers, None when it can't be read and
on other systems. On a GDI driver, reached through Windows' XPS-to-GDI conversion, a page with
transparency prints with halos, as black boxes or not at all (storytold/pdfcraft#6155, #5838,
#5940), so PdfCraft will flatten it for those drivers only.
The Windows end-to-end test checks the CI queue's "Generic / Text Only" driver reads as GDI.
* Test: the GDI-driver check in a helper (keeps the end-to-end test under the complexity limit)
* winprint bc06a7c48b768eb27a828c7986f6d2868b245ee0: storytold/winprint.rs main with #21 (PrinterDevice::is_xps_driver)