Wallpapers are downscaled when the displayscaling is turned up

[peterkrull]

To reproduce, apply 200% scaling to a monitor, and its wallpaper will be scaled down by 1/2 becoming blurry.

The issue seems to be that the width and height of logical_size within smithay_client_toolkit::output::OutputInfo does not actually represent the number of pixels on the display, but this is being used when calculating the new size of the scaled wallpaper.