Add additional shader variant for HDR support

Both qsb and the batch renderer will generate and use the rewritten
shader for this new variant respectively.

Task-number: QTBUG-126035
Change-Id: I5c4078afcfb22de1e82485459c58d2211958ab7b
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

src/gui/rhi/qshader.cpp

@@ -215,6 +215,9 @@ QT_BEGIN_NAMESPACE
     translated to a compute shader that may be dependent on the index buffer
     usage in the draw calls (e.g. if the shader is using gl_VertexIndex), hence
     the need for three dedicated variants.
+
+    \value [since 6.10] HdrCapableFragmentShader A fragment shader rewritten to support high
+    dynamic range rendering in a Qt Quick scenegraph.
  */
 
 /*!

src/gui/rhi/qshader.h

@@ -105,7 +105,8 @@ public:
         BatchableVertexShader,
         UInt16IndexedVertexAsComputeShader,
         UInt32IndexedVertexAsComputeShader,
-        NonIndexedVertexAsComputeShader
+        NonIndexedVertexAsComputeShader,
+        HdrCapableFragmentShader,
     };
 
     enum class SerializedFormatVersion {