`currentBinlogEntry.OriginalSize` should not be increased if the event is going to be ignored

	if b.currentBinlogEntry != nil {
		b.currentBinlogEntry.OriginalSize += len(ev.RawData)
	}

Previously we use len(ev.RawData) to determine a event size

• Calculate size for all fields in a row event is hard
• Either an event not in ReplicateDoDb/Tb or not passing 'where filter'
• To ignore size of rows not passing where filter', we need row size instead of event size
  • Use estimation: avg_row_size = event_size / row_count

Original case

1. job: replicate table a.a
2. In incremental stage, commit large transaction on an irrelevant table.
   • E.g. delete from a.b, where a.b has lots of rows.
3. The job goes error Too much entriesSize , not enough memory

Reason:

• We limit entriesSize to prevent dtle OOM crash
• entriesSize is larger than it actually is
  • size of some entries has not been ignored