Modify BinlogReader to process transactions via buffer

DBZ-390 has shown that the replication log can contain rolled-back transactions. We cannot stream the transaction directly into the Kafka but we need to buffer events before BEGIN and COMMIT. Only if transaction is completed with COMMIT we will stream it to Kafka from the buffer.
We will store the events temporarily into a bounded buffer with a configurable capacity. When the transaction is committed we will play it from the buffer.
It is necessary to be careful with offset commits to make sure that the recovery is reliable and no data are lost when in memory state is lost on a connector restart.