IVGCVSW-3419 Add reference workload support for the new Stack layer

 * Added reference workload for the Stack layer
 * Added factory methods
 * Added validation support
 * Added unit tests

Signed-off-by: Matthew Jackson <matthew.jackson@arm.com>
Change-Id: Ib14b72c15f53a2a2ca152afc357ce2aa405ccc88
diff --git a/src/backends/reference/workloads/CMakeLists.txt b/src/backends/reference/workloads/CMakeLists.txt
index 696605d..c9db057 100644
--- a/src/backends/reference/workloads/CMakeLists.txt
+++ b/src/backends/reference/workloads/CMakeLists.txt
@@ -109,6 +109,8 @@
     RefSpaceToDepthWorkload.hpp
     RefSplitterWorkload.cpp
     RefSplitterWorkload.hpp
+    RefStackWorkload.cpp
+    RefStackWorkload.hpp
     RefStridedSliceWorkload.cpp
     RefStridedSliceWorkload.hpp
     RefTransposeConvolution2dWorkload.cpp
@@ -127,6 +129,8 @@
     SpaceToDepth.cpp
     Splitter.hpp
     Splitter.cpp
+    Stack.cpp
+    Stack.hpp
     StridedSlice.hpp
     StridedSlice.cpp
     StringMapping.cpp