Fix ext function caching

[Flyangz]

Describe the bug
After upgrading to DataFusion 49 #1154 , the expression cache (cached_exprs_evaluator) fails to deduplicate identical extension functions.
This is because DataFusion's SimpleScalarUDF::equals now enforces pointer equality (Arc::ptr_eq) for function implementations (DataFusion PR #16781). Auron currently creates a new Arc for every UDF instance （native-engine/datafusion-ext-functions/src/lib.rs）, causing logically identical functions to have different memory addresses.

To Reproduce
Run the following query with logging the dups in cached_exprs_evaluator.rs shows 0 duplicates found.

test("my test") {
    withTable("my_table") {
      sql("""
            |create table my_cache_table using parquet as
            |select col1 from values (''{"a":"1", "b":"2"}'), ('{"a":"3", "b":"4"}'), ('{"a":"5", "b":"6"}')
            |""".stripMargin)
      sql("""
            |select 
            |       get_json_object(col1, '$.a'),
            |       get_json_object(col1, '$.b')
            |from my_cache_table
            |""".stripMargin).show()
    }
  }

Expected behavior

Screenshots

Additional context