Implement DEFAULT CURRENT_TIMESTAMP and ON UPDATE CURRENT_TIMESTAMP for kudu

Implement DEAULT CURRENT_TIMESTAMP and ON UPDATE CURRENT_TIMESTAMP just like in MYSQL. 
Here is the reference.
https://dev.mysql.com/doc/refman/8.0/en/timestamp-initialization.html

This feature can be helpful when user want an automatic timestamp column and
can be used for further TTL.

It works like this:
1. Whether DEFAULT CURRENT_TIMESTAMP is set or ON UPDATE CURRENT_TIMESTAMP is set, will create a timestamp column for table.
2. If only DEFAULT CURRENT_TIMESTAMP is set, then will get kudu time when insert.
3. If only ON UPDATE CURRENT_TIMESTAMP is set, then it will have default value and will update timestamp column when update.
4. If both set, then it will get kudu time when insert and update timestamp when update.