Geometry Nodes: Improve viewer node domain choice for blur node

Add preferred domain based on the "Value" input field. Most often,
the domain must match the original domain for the value.

Differential Revision: https://developer.blender.org/D16730

source/blender/nodes/geometry/nodes/node_geo_blur_attribute.cc

@@ -14,6 +14,7 @@
 
 #include "BKE_attribute_math.hh"
 #include "BKE_curves.hh"
+#include "BKE_geometry_fields.hh"
 #include "BKE_mesh.h"
 #include "BKE_mesh_mapping.h"
 
@@ -443,6 +444,11 @@ class BlurAttributeFieldInput final : public bke::GeometryFieldInput {
     }
     return false;
   }
+
+  std::optional<eAttrDomain> preferred_domain(const GeometryComponent &component) const override
+  {
+    return bke::try_detect_field_domain(component, value_field_);
+  }
 };
 
 static StringRefNull identifier_suffix(eCustomDataType data_type)