Provide QPdfDocument rotation information

Some PDF files use page rotation: for instance, a document using the A4 paper format in landscape mode.

While displaying is correct with QPdfDocument rendering, this can be a problem if trying to actually print the PDF file with QPrinter, since the actual orientation has to be "guessed" considering the aspect ratio of the document's pagePointSize(), which would just be an unacceptable assumption for arbitrary paper sizes of the source document (for example, a custom page size that seems in landscape mode, but is just wider than taller).

If rotation information is given (which seems possible from the Pdfium API), it would make things easier since the dev would then be able to properly set the page size and rotation in the renderer and/or set the printer orientation accurately.