[Kernel] Remove the protocol specific conversions from JsonHandler.parseJSON

[vkorukanti]

Feature request

Currently the JsonHandler.parseJson parses the stats values. Some of these values are for columns of type TIMESTAMP, DATE which are not native types in Json. Exactly how the string format of the TIMESTAMP, DATE can be interpreted depends on the Delta protocol details. We want to change it as follows:

1. JsonHandler.parseJson just parses as native json types
2. Kernel-API module applies expressions on the parsed JSON values to convert them to appropriate types.

[SemyonSinchenko]

Hello! I would be willing to contribute. Do I understand right, that changes should be done:

• in io.delta.kernel.defaults.internal.data.DefaultJsonRow.decodeElement(JsonNode jsonValue, DataType dataType) I need to return String (jsonValue.textValue()) for "date" / "timestamp with tz" and Instant for "timestamp"
• Applying expressions in this case should be moved to default implementation of ColumnarBatch? I see that JsonHandler.parseJson returns ColumnarBatch but I lost a little what happens after...

Thanks in advance for any advice/clue how to implement it!