Converting the LCMS2 transform to a 3D LUT early causes issues:
- It's a lossy process, the consumer will not be able to pick a
3D LUT size on their own.
- It requires unnecessary conversions and allocations: an intermediate
3D LUT is allocated, but the renderer already allocates one.
- It makes it harder to support arbitrary color transforms in the
renderer, because each type needs to be handled differently.
Instead, expose a function to evaluate a color transform, and use
that to build the 3D LUT in the renderer.
It's cumbersome for compositors to guard every
wlr_color_transform_ref() or wlr_color_transform_unref() call
behind a #if WLR_HAS_COLOR_MANAGEMENT. Moreover, none of the LCMS2
types are used in our public API.
Instead, always install the color.h header, and add a stub for
wlr_color_transform_init_linear_to_icc().
