Implemented the custom 3D LUT feature in the ColorGrading API, allowing
users to specify a custom LUT for final color mapping.
To test this feature, added a "Custom LUT" option to the color grading
settings in the gltf_viewer sample. This includes several procedurally
generated LUTs for testing purposes:
- Negative
- Grayscale
- Sepia
- Teal and Orange
Updated settings serialization (Settings.cpp) and the viewer UI
(ViewerGui.cpp) to support these options.
FIXES=[362596936]
84dc1b1c43