PSD: support native CMYK introduced by Qt 6.8

Qt 6.8 will introduce native support for the CMYK (8-bit) format.
With this patch you will finally be able to correctly see the colors of CMYK images with ICC profile.
The testing part has been updated with the addition of an (optional) json file for each image to test. Inside you enter which image to use depending on the Qt version.

In short:
- Added native CMYK suport to PSD reader
- CMYK with alpha is converted using QColorSpace in a RGBA image
- Read tests changed to use the correct comparison image based on the Qt version
- Fixed also XCF tests: now works with all Qt version (see also [QTBUG-120614](https://bugreports.qt.io/browse/QTBUG-120614))
- Work around for CCBUG: 468288

autotests/CMakeLists.txt

@@ -11,7 +11,7 @@ macro(kimageformats_read_tests)
     endif()
 
     if (NOT TARGET readtest)
-        add_executable(readtest readtest.cpp)
+        add_executable(readtest readtest.cpp templateimage.cpp)
         target_link_libraries(readtest Qt6::Gui)
         target_compile_definitions(readtest
             PRIVATE IMAGEDIR="${CMAKE_CURRENT_SOURCE_DIR}/read")