Try harder to ensure model Print to PDF temporary file gets deleted eventually

Currently DiagramPrinter tries once to delete the temporary xxxx.pdf.tmp file generated by the original PDF printing that does not include page numbers. The page numbering logic will then generate the final .pdf file and after that the .pdf.tmp file is attempted to be deleted.

This deletion seems to be failing all the time which is a clear indication that some kind of file handle is left open to the .pdf.tmp file after the page numbering procedure. Without running the page numbering logic, the temporary file can be successfully deleted immediately.

The page numbering uses PdfCopy which internally is probably using memory mapping. Our code is closing all the classes which can be closed but something is left open until the GC collects it and only then the .pdf.tmp file can be deleted successfully.