Skip unnecessary json.Unmarshal in converter

[SpencerTorres]

An optimization when loading object/array-like types dependent on jsonConverter. We can skip this marshal+unmarshal combo and simply marshal it and cast the result to the required json.RawMessage.

Looks like this was added to convert []byte to json.RawMessage, but both types are already []byte so we can simply cast it.

Changes:

• optimized jsonConverter
• updated changelog

[aangelisc]

@SpencerTorres this just needs main merged and then it's good to go 😊

[aangelisc]

Thanks @SpencerTorres!