Allow parsing a LUT from a memory buffer rather than a file

OCIO's LUT file parsing is set up to work from files on disk. It would be very helpful to be able to have a function that would take a memory buffer and use the LUT parsers to turn it into a GroupTransform.

There is a way to do this already using the recent ConfigIOProxy class. However, it takes a fair amount of code and a fair amount of OCIO expertise to write it. This task is to write that code and turn it into a parseFromBuffer method on the GroupTransform class.

The unit tests for ConfigIOProxy in Config_tests.cpp provide some good sample code that could be used as a starting point.

Comienza con las pruebas unitarias de ConfigIOProxy en Config_tests.cpp y luego sigue cómo GroupTransform utiliza actualmente los analizadores LUT para archivos. Implementa y expón GroupTransform::parseFromBuffer usando el enfoque existente basado en búferes, y añade cobertura que demuestre que una LUT almacenada en un búfer de memoria produce la GroupTransform esperada.

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