wayland: Implement fractional_scale_v1 protocol
Giving clients hints about optimal fractional scaling ratios,
to be used together with the wp_viewport
protocol.
See also:
- https://gitlab.freedesktop.org/wayland/wayland-protocols/-/blob/1.31/staging/fractional-scale/fractional-scale-v1.xml
- !2726 (merged)
- !2771 (merged)
Can be tested with: