[FLINK-36647][transform] Support Timestampdiff and Timestampadd function in cdc pipeline transform

[aiwenmo]

Support TimestampDiff function in cdc pipeline transform.

Now. The TimestampDiff function implemented in the current code of CDC is as follows:

TIMESTAMP_DIFF('DAY', TO_TIMESTAMP('1970-01-01 00:00:00'), TO_TIMESTAMP('1970-01-02 00:00:00')) = 1 

The Timestampdiff and Timestampadd function implemented in Flink SQL is as follows:

SQL Function	Table Function
TIMESTAMPDIFF(timepointunit, timepoint1, timepoint2)	timestampDiff(TIMEPOINTUNIT, TIMEPOINT1, TIMEPOINT2)	Returns the (signed) number of timepointunit between timepoint1 and timepoint2. The unit for the interval is given by the first argument, which should be one of the following values: SECOND, MINUTE, HOUR, DAY, MONTH, or YEAR.
TIMESTAMPADD(timeintervalunit, interval, timepoint)	N/A

I have implemented the Timestampdiff and Timestampadd function with the same definition as Flink.

TIMESTAMPDIFF(DAY, TO_TIMESTAMP('1970-01-01 00:00:00'), TO_TIMESTAMP('1970-01-02 00:00:00')) = 1  
TIMESTAMPADD(DAY, 1, TO_TIMESTAMP('1970-01-02 00:00:00'))