[CK_BUILDER] Add backward weight instance traits for xdl cshuffle. (#3143)

* Add backward weight instance traits for xdl cshuffle.

To keep instance test file sizes reasonable, we start a new test_bwd_weight_instances_traits.cpp test file.

* Fix copyright notices.

* Remove (c) symbol, replace with (C).

Having UTF-8 in source caused an error with code generation.

include/ck/tensor_operation/gpu/device/impl/device_grouped_conv_bwd_weight_xdl_cshuffle.hpp

@@ -1,5 +1,5 @@
+// Copyright (C) Advanced Micro Devices, Inc., or its affiliates.
 // SPDX-License-Identifier: MIT
-// Copyright (c) 2018-2025, Advanced Micro Devices, Inc. All rights reserved.
 
 #pragma once
 
@@ -24,6 +24,10 @@
 #include "ck/host_utility/device_prop.hpp"
 #include "ck/host_utility/kernel_launch.hpp"
 
+#ifdef CK_EXPERIMENTAL_BUILDER
+#include "ck_tile/builder/reflect/instance_traits_device_grouped_conv_bwd_weight_xdl_cshuffle.hpp"
+#endif
+
 namespace ck {
 namespace tensor_operation {
 namespace device {
@@ -1225,6 +1229,19 @@ struct DeviceGroupedConvBwdWeight_Xdl_CShuffle
         return str.str();
     }
 
+#ifdef CK_EXPERIMENTAL_BUILDER
+    std::string GetInstanceString() const override
+    {
+        static_assert(ck_tile::reflect::HasInstanceTraits<DeviceOp>,
+                      "Specialization of instance_traits not found. Please check that a "
+                      "specialization exists in file "
+                      "ck_tile/builder/reflect/"
+                      "instance_traits_device_grouped_conv_bwd_weight_xdl_cshuffle.hpp "
+                      "for the given template parameters.");
+        return ck_tile::reflect::instance_string<DeviceOp>();
+    }
+#endif
+
     size_t GetWorkSpaceSize(const BaseArgument* p_arg) const override
     {
         auto arg = dynamic_cast<const Argument*>(p_arg);