opengl: add support for GL_EXT_YUV_target on Android

GL_EXT_YUV_target¹ provides a way to access an external texture without applying a conversion to RGBA texture, which can be used to supply our own matrices for conversion.

This can be used to workaround bogus RGBA conversion for some devices and can help integrating better with deinterlacing, or in general plane filtering, and some YUV pipeline like encoding.

Draft since limiting this to Quest 3 is required here for now and some tests on Quest 3 are required, as well as multiple input space/transfer/source.

• Fixes vlc-unity#236 (closed) by workarounding the YUV to RGB conversion
• Refs !6391 (closed)

1. https://registry.khronos.org/OpenGL/extensions/EXT/EXT_YUV_target.txt ↩