[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

Author: Daoyuan Wang <daoyuan.wang@intel.com>

Closes #2458 from adrian-wang/timestamp and squashes the following commits:

4274b1d [Daoyuan Wang] set test not related to timezone
1234f66 [Daoyuan Wang] fix timestamp smaller than 0 and cast int as timestamp