Add tests to ensure DelayedEncodeData is serialized properly

[BellringerQuinn]

With the Unity SDK, we recently encountered errors related to DelayedEncodeData json serialization.

The DelayedEncodeData object allows you to include an object[], args. These args can be anything from ints to strings to complex objects with multiple fields to arrays. Any complex object must have their fields serialized alphabetically.

In the Unity SDK, we added this test https://github.com/0xsequence/sequence-unity/blob/master/Assets/SequenceSDK/WaaS/Tests/DelayedEncodeJsonSerializationTest.cs and modified the JSON serializer logic until it would pass the test.

This potential bug may pop up for clients who use complex contracts and can be hard to diagnose/identify. Let's add a test (and correct behaviour if necessary) for the Unreal SDK to avoid future headaches