Add ColorSpace::createLUT

Generates a 3D LUT of a specified size. The generated LUT is meant to
be used as a 3D OpenGL texture for fast color space conversions in
shaders. This will be used to convert from P3 bitmaps to scRGB.

Bug: 32984164
Test: colorspace_test
Change-Id: I01f7276f885c71bde480e79260013d62786b377c