[wallpapers/image] Look for wallpaper for the device's physical size
When using PLASMA_USE_QT_SCALING=1, the sizes returned here are
automatically scaled down to be the logical size, taking into account
the scale factor. However this is not what we want; in this case, we
want to choose a wallpaper that matches the screen's physical size,
not its logical size, or else it will be too small and look blurry.
To accomplish this, we need to multiply the returned width and height
values by the device pixel ratio. When using PLASMA_USE_QT_SCALING=1,
this is set to the correct value, so multiplying by it will produce the
correct final size.
BUG: 423563 FIXED-IN: 5.19.3