Correct methods and variables names which uses writeId instead of transactionId.

Per table write ID implementation (HIVE-18192) have replaced global transaction ID with per table write ID to version the data files in a table.

Now, the ACID data files referred by different class methods and variables still uses names transactionId to mean write id. 

So, it is required to rename those methods/variables/classes to mean writeId instead of transactionId.