[spark] Integrate Variant with Spark4

[Zouxxyy]

Purpose

Subtask of #4471

• Integrate Variant with Spark4

CREATE TABLE t (v VARIANT) USING paimon;

INSERT INTO t VALUES parse_json('{"age":26,"city":"Beijing"}');

SELECT variant_get(v, '$.age', 'int') FROM t;

Tests

API and Format

Documentation

[JingsongLi]

+1