The "single pixel buffer" Wayland protocol extension provides a way for
clients to create 1x1 buffers with a single color, specified by
providing the color channels (red, green and blue) as well as the
alpha channel as a 32 bit unsigned integer.
For now, this is turned into a 1x1 texture. Future potential
improvements is to hook things up to the scanout candidate logic and
turn it into a scanout capable DMA buffer.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2246>
