Add tool to generate color space conversion 3D LUTs

The tool needs to be run on an Android device and must be compiled
manually (i.e. it's not compiled as part of a regular Android build).

The tool outputs 3D LUTs in a format that can be included directly
in a C/C++ file/header.

Bug: 32984164
Test: ran lutgen and checked output
Change-Id: I96f7d0d088965c3b63c0fb4079ddeaeee7246418