Adding modified commit start time in the MySQL connector

For generating the denormalized view of the data residing in multiple MySQL systems, timestamp is the key which can be used for alignment. 

MySQL connector emits the processing time with each binlog record. The processing time is the time when the query was actually submitted in the transaction. Using processing time for denormalization can lead to many problems. For solving this, we are introducing modified commit start time in each binlog payload.

Detailed design:

https://docs.google.com/document/d/1y86FWcrk55Ohpvzqo0d8s56MsCdUICsCT76g1Gt3sWM/edit#