IVGCVSW-3420 Add Serialization support for the new Stack layer

 * Adds serialization/deserialization support
 * Adds related unit test

Signed-off-by: Matthew Jackson <matthew.jackson@arm.com>
Change-Id: I69deb5397b8a06c679715e24971e9bb1c282140d
diff --git a/src/armnnSerializer/ArmnnSchema.fbs b/src/armnnSerializer/ArmnnSchema.fbs
index 0918792..e3953df 100644
--- a/src/armnnSerializer/ArmnnSchema.fbs
+++ b/src/armnnSerializer/ArmnnSchema.fbs
@@ -130,7 +130,8 @@
     SpaceToDepth = 40,
     Prelu = 41,
     TransposeConvolution2d = 42,
-    Resize = 43
+    Resize = 43,
+    Stack = 44
 }
 
 // Base layer table to be used as part of other layers
@@ -599,6 +600,17 @@
     dataLayout:DataLayout;
 }
 
+table StackLayer {
+    base:LayerBase;
+    descriptor:StackDescriptor;
+}
+
+table StackDescriptor {
+    axis:uint;
+    numInputs:uint;
+    inputShape:[uint];
+}
+
 union Layer {
     ActivationLayer,
     AdditionLayer,
@@ -643,7 +655,8 @@
     SpaceToDepthLayer,
     PreluLayer,
     TransposeConvolution2dLayer,
-    ResizeLayer
+    ResizeLayer,
+    StackLayer
 }
 
 table AnyLayer {