issue #23555 - watermarks scaled incorrectly on Macs

issue #23555
Fixed by scaling the watermark to device resolution when writing it to the paint device. Generating the watermark at device resolution fails with memory allocation errors, among other problems.
It's unclear why this manifested only on Macs. One hypothesis is that print drivers on Macs handle printer resolution differently (we know Mac PDFs are larger than other platforms).
Tested on Mac and Linux with openrpt/OpenRPT/data/test2.xml.