IVGCVSW-3878 Add reference workload for SLICE

* Added reference workload implementation and layer tests
  for all supported tensor dimensions (1d, 2d, 3d, 4d)

Signed-off-by: Aron Virginas-Tar <Aron.Virginas-Tar@arm.com>
Change-Id: I40eb300828933e9183027281105d1a7e597d1569
diff --git a/src/backends/reference/backend.mk b/src/backends/reference/backend.mk
index b1f0a03..b2ec748 100644
--- a/src/backends/reference/backend.mk
+++ b/src/backends/reference/backend.mk
@@ -69,6 +69,7 @@
         workloads/RefResizeBilinearWorkload.cpp \
         workloads/RefResizeWorkload.cpp \
         workloads/RefRsqrtWorkload.cpp \
+        workloads/RefSliceWorkload.cpp \
         workloads/RefSoftmaxWorkload.cpp \
         workloads/RefSpaceToBatchNdWorkload.cpp \
         workloads/RefSpaceToDepthWorkload.cpp \
@@ -78,6 +79,7 @@
         workloads/RefTransposeConvolution2dWorkload.cpp \
         workloads/Resize.cpp \
         workloads/Rsqrt.cpp \
+        workloads/Slice.cpp \
         workloads/SpaceToBatchNd.cpp \
         workloads/SpaceToDepth.cpp \
         workloads/Stack.cpp \