Support Map Type in JSONExtract

Why it matters

This feature enables users to directly extract JSON objects as Map types, allowing more convenient and type-safe handling of JSON key-value data within ClickHouse queries.

How to use it

Use the JSONExtract function with the target type set to Map to extract JSON objects from string columns. For example:

SELECT JSONExtract(your_json_column, 'Map(String, Int32)') FROM your_table;