Color Management: Change byte color attributes to always be sRGB

These don't really work as scene linear with sRGB transfer function for e.g.
ACEScg, there are not enough bits. If you want wide gamut you need to use
float colors.

Pull Request: https://projects.blender.org/blender/blender/pulls/145763

intern/cycles/kernel/geom/attribute.h

@@ -6,6 +6,7 @@
 
 #include "kernel/globals.h"
 #include "kernel/types.h"
+#include "kernel/util/colorspace.h"
 
 #include "util/color.h"
 
@@ -123,8 +124,9 @@ ccl_device_inline T attribute_data_fetch_bytecolor(KernelGlobals /*kg*/, int /*o
 
 ccl_device_template_spec float4 attribute_data_fetch_bytecolor(KernelGlobals kg, int offset)
 {
-  return color_srgb_to_linear_v4(
+  const float4 rec709 = color_srgb_to_linear_v4(
       color_uchar4_to_float4(kernel_data_fetch(attributes_uchar4, offset)));
+  return make_float4(rec709_to_rgb(kg, make_float3(rec709)), rec709.w);
 }
 
 ccl_device_template_spec Transform attribute_data_fetch(KernelGlobals kg, int offset)