Fixes ProtobufSerializer's reversed list of message indexes (#2507)

Co-authored-by: Matthew Miller <[email protected]>
Co-authored-by: Robert Yokota <[email protected]>

Author: 3 people

src/Confluent.SchemaRegistry.Serdes.Protobuf/ProtobufSerializer.cs

@@ -148,6 +148,9 @@ private static List<int> CreateIndexArray(MessageDescriptor md)
                 throw new InvalidOperationException("MessageDescriptor not found.");
             }
 
+            // The indexes are built in reverse order, so reverse them to get the correct order
+            indices.Reverse();
+
             return indices;
         }