This returns an EventReader which extracts entries from the src event stream and returns the entries as RawV4Event objects. The src stream can be a binary log event stream or a relay log event stream. NOTE: This reader assumes there is no binlog magic marker at the beginning of the stream. It also assumes the event entries are serialized using v4 binlog format. Finally, this reader does not set sizes for extra headers, fixed length data, and checksum (i.e. event.VariableLengthData() will return the entire event payload).