Do not sort keys during json serialization

[jonmmease]

Closes #3380

This PR removes the instruction to the json/orjson engines to sort dict keys during serialization. This fixes #3380 and should improve serialization performance a little.

Also, while looking at the orjson option flags, I noticed that there is a OPT_NON_STR_KEYS option.

Serialize dict keys of type other than str. This allows dict keys to be one of str, int, float, bool, None, datetime.datetime, datetime.date, datetime.time, enum.Enum, and uuid.UUID. For comparison, the standard library serializes str, int, float, bool or None by default.

This would have been a better fix that what I did in #3351, so I made the change here.

[nicolaskruchten]

@jonmmease is this one ready for review?

[jonmmease]

yes