Fix misplacement of some non-PDF annotations on hiDPI

PagePainter::drawShapeOnImage() and drawEllipseOnImage() didn’t respect the image’s device pixel ratio.

Steps to reproduce:
* Set your screen scale to e. g. 1.25.
* Open e. g. a .txt document.
* Draw e. g. an arrow annotation or a text markup annotation.
2 jobs for master in 14 minutes and 2 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed #59820
clang_format

00:03:31

passed #59819
linux kf5-qt5 qt5.12

00:14:02

44.0%