644fb2b679 fixed a long standing issue
that offscreen example showed the wrong colors. However the fix assumes
that input texture color space is always sRGB.
This adds a shader variation that draws textures that are stored in scene referred
linear color space (like all of our Image data-block).
Co-authored-by: Clément Foucault <foucault.clem@gmail.com>
Pull Request: https://projects.blender.org/blender/blender/pulls/147788
e2dc63c5de