Add night adaptation control to ColorGrading (#4559)

In low-light conditions, peak luminance sensitivity of the eye shifts
toward the blue end of the visible spectrum. This effect called the
Purkinje effect occurs during the transition from photopic (cone-based)
vision to scotopic (rod-based) vision. Because the rods and cones use the
same neural pathways, a color shift is introduced as the rods take over to
improve low-light perception.

This function aims to (somewhat) replicate this color shift and peak
luminance sensitivity increase to more faithfully reproduce scenes in
low-light conditions as they would be perceived by a human observer
(as opposed to an artificial observer such as a camera sensor).

The night adaptation can be controlled using a 0..1 factor for artistic
reasons: `ColorGrading::Builder::nightAdaptation()`.

libs/viewer/src/SimpleViewer.cpp

@@ -214,6 +214,7 @@ static void colorGradingUI(Settings& settings, float* rangePlot, float* curvePlo
         ImGui::Checkbox("Gamut mapping", &colorGrading.gamutMapping);
 
         ImGui::SliderFloat("Exposure", &colorGrading.exposure, -10.0f, 10.0f);
+        ImGui::SliderFloat("Night adaptation", &colorGrading.nightAdaptation, 0.0f, 1.0f);
 
         if (ImGui::CollapsingHeader("White balance")) {
             int temperature = colorGrading.temperature * 100.0f;