IVGCVSW-3539 Add CL support and tests for Stack

* Added CL backend support for Stack
* Added unit tests for Stack on the CL backend
* Refactored unit tests to support generic data types

Signed-off-by: Matthew Jackson <matthew.jackson@arm.com>
Change-Id: I38ee3e9d8947ea98a3104c982698001e704d7d89
diff --git a/src/backends/cl/ClWorkloadFactory.cpp b/src/backends/cl/ClWorkloadFactory.cpp
index 6ce87d8..4a593aa 100644
--- a/src/backends/cl/ClWorkloadFactory.cpp
+++ b/src/backends/cl/ClWorkloadFactory.cpp
@@ -433,4 +433,10 @@
     return MakeWorkload<ClSpaceToDepthWorkload>(descriptor, info);
 }
 
+std::unique_ptr<IWorkload> ClWorkloadFactory::CreateStack(const StackQueueDescriptor& descriptor,
+                                                          const WorkloadInfo& info) const
+{
+    return MakeWorkload<ClStackWorkload>(descriptor, info);
+}
+
 } // namespace armnn