handle visual observations with onnx

com.unity.ml-agents/Runtime/Inference/BarracudaModelParamLoader.cs

             var heightBp = shape[0];
             var widthBp = shape[1];
             var pixelBp = shape[2];
-            var heightT = tensorProxy.shape[1];
-            var widthT = tensorProxy.shape[2];
-            var pixelT = tensorProxy.shape[3];
+            var heightT = tensorProxy.Height;
+            var widthT = tensorProxy.Width;
+            var pixelT = tensorProxy.Channels;
             if ((widthBp != widthT) || (heightBp != heightT) || (pixelBp != pixelT))
             {
                 return $"The visual Observation of the model does not match. " +

com.unity.ml-agents/Runtime/Inference/TensorProxy.cs

         public Type DataType => k_TypeMap[valueType];
         public long[] shape;
         public Tensor data;
+
+        public long Height
+        {
+            get { return shape.Length == 4 ? shape[1] : shape[5]; }
+        }
+
+        public long Width
+        {
+            get { return shape.Length == 4 ? shape[2] : shape[6]; }
+        }
+
+        public long Channels
+        {
+            get { return shape.Length == 4 ? shape[3] : shape[7]; }
+        }
     }
 
     internal static class TensorUtils
             tensor.data?.Dispose();
             tensor.shape[0] = batch;
 
-            if (tensor.shape.Length == 4)
+            if (tensor.shape.Length == 4 || tensor.shape.Length == 8)
-                        (int)tensor.shape[1],
-                        (int)tensor.shape[2],
-                        (int)tensor.shape[3]));
+                        (int)tensor.Height,
+                        (int)tensor.Width,
+                        (int)tensor.Channels));
             }
             else
             {