IVGCVSW-4259 Add frontend and reference workload for UnaryOperationLayer

* Added new layer named ElementwiseUnary
* Deprecated existing Abs/Rsqrt layer functions
* Updated existing Abs/Rsqrt test infrastructure to use new layer
* Added boilerplate for new Exp,Neg,Sqrt elemwise op layers
* AbsQuantize test removed pending future commit
* Serialization support added

!android-nn-driver:2550

Change-Id: Ic595c645925e17b45db568187fd05646daf2e87f
Signed-off-by: josh minor <josh.minor@arm.com>
diff --git a/src/backends/reference/backend.mk b/src/backends/reference/backend.mk
index 5f9af59..412dc94 100644
--- a/src/backends/reference/backend.mk
+++ b/src/backends/reference/backend.mk
@@ -21,7 +21,6 @@
         RefWorkloadFactory.cpp \
         RefRegistryInitializer.cpp \
         RefTensorHandleFactory.cpp \
-        workloads/Abs.cpp \
         workloads/Activation.cpp \
         workloads/ArgMinMax.cpp \
         workloads/BatchNormImpl.cpp \
@@ -43,7 +42,6 @@
         workloads/Pad.cpp \
         workloads/Pooling2d.cpp \
         workloads/PreluImpl.cpp \
-        workloads/RefAbsWorkload.cpp \
         workloads/RefActivationWorkload.cpp \
         workloads/RefArgMinMaxWorkload.cpp \
         workloads/RefBatchNormalizationWorkload.cpp \
@@ -60,6 +58,7 @@
         workloads/RefDequantizeWorkload.cpp \
         workloads/RefDetectionPostProcessWorkload.cpp \
         workloads/RefElementwiseWorkload.cpp \
+        workloads/RefElementwiseUnaryWorkload.cpp \
         workloads/RefFakeQuantizationFloat32Workload.cpp \
         workloads/RefFloorWorkload.cpp \
         workloads/RefFullyConnectedWorkload.cpp \
@@ -78,7 +77,6 @@
         workloads/RefReshapeWorkload.cpp \
         workloads/RefResizeBilinearWorkload.cpp \
         workloads/RefResizeWorkload.cpp \
-        workloads/RefRsqrtWorkload.cpp \
         workloads/RefSliceWorkload.cpp \
         workloads/RefSoftmaxWorkload.cpp \
         workloads/RefSpaceToBatchNdWorkload.cpp \
@@ -88,7 +86,6 @@
         workloads/RefSplitterWorkload.cpp \
         workloads/RefTransposeConvolution2dWorkload.cpp \
         workloads/Resize.cpp \
-        workloads/Rsqrt.cpp \
         workloads/Slice.cpp \
         workloads/SpaceToBatchNd.cpp \
         workloads/SpaceToDepth.cpp \