Fix color distortion in low light conditions

[azeey]

🦟 Bug fix

Summary

This replaces the gamma correction QML element and instead tells Qt to copy the texture as is without decoding from srgb->rgb. This is an alternative to #629

Using Renderdoc, I found that no matter what the target render texture is (RGBA8_UNORM_SRGB or RGBA8_UNORM), the back color buffer (what Qt displays on the screen) always converts it to RGB8_UNORM. I also found that there's a parameter that can be set on a texture to tell OpenGL to not do any srgb->linear conversion https://docs.imgtec.com/reference-manuals/open-gl-es-extensions/html/topics/GL_EXT/texture-sRGB-decode.html

This fixes various distortion issues. Here are some examples:

Banding in specular highlights

Before

After

Color distortion in low light conditions

Before

After

Additional information in https://github.com/azeey/gz-rendering-benchmark/tree/main/gamma_correction

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[azeey]

cc @athenaz2