fix: uses the json node clone API to avoid unecessary allocs

Author: baywet

src/Microsoft.OpenApi/Helpers/JsonNodeCloneHelper.cs

@@ -1,40 +1,15 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license.
 
-using System.Text.Json;
 using System.Text.Json.Nodes;
-using System.Text.Json.Serialization;
-using Microsoft.OpenApi.Any;
 
 namespace Microsoft.OpenApi.Helpers
 {
     internal static class JsonNodeCloneHelper
     {
-        private static readonly JsonSerializerOptions options = new()
-        {
-            ReferenceHandler = ReferenceHandler.IgnoreCycles
-        };
-
         internal static JsonNode Clone(JsonNode value)
         {
-            var jsonString = Serialize(value);
-            if (string.IsNullOrEmpty(jsonString))
-            {
-                return null;
-            }
-
-            var result = JsonSerializer.Deserialize<JsonNode>(jsonString, options);
-            return result;
-        }
-
-        private static string Serialize(object obj)
-        {
-            if (obj == null)
-            {
-                return null;
-            }
-            var result = JsonSerializer.Serialize(obj, options);
-            return result;
+            return value.DeepClone();
         }
     }
 }