When the logical layout mode is used, allow configuring the scaling to
be non-integer. Supported scales are so far hard coded to include at
most 1, 1.5 and 2, and scales that doesn't result in non-fractional
logical monitor sizes are discarded.

Wayland outputs are set to have scale ceil(actual_scale) meaning well
behaving Wayland clients will provide buffers with buffer scale 2, thus
being scaled down to the fractional scale.

https://bugzilla.gnome.org/show_bug.cgi?id=765011