[SPARK-3598][SQL]cast to timestamp should be the same as hive

this patch fixes timestamp smaller than 0 and cast int as timestamp

select cast(1000 as timestamp) from src limit 1;

should return 1970-01-01 00:00:01, but we now take it as 1000 seconds.
also, current implementation has bug when the time is before 1970-01-01 00:00:00.
@rxin @marmbrus @chenghao-intel