mysqlbinlog can produce events larger than max_allowed_packet

MDEV-10963 did not cover a case of to be fragmented Rows_log_event is not the final one
from its parent sql statement.

If one executes the following one a MariaDB server with "log_bin=1"
create or replace table t1 (a int primary key, b varchar(1024)) engine=innodb;
insert into t1 select seq,repeat("a",1024) from seq_1_to_100000

The generated binary log has an entry:
BINLOG '
BoA2ZRMBAAAAMAAAAPcBAAAAABIAAAAAAAEABHRlc3QAAnQxAAIDDwIABAJW98rq
BoA2ZRcBAAAAUhwAAEkeAAAAABIAAAAAAAAAAv/8AQAAAAAEYWFhYWFhYWFhYWFhYWFhYWFhYWFh
YWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFh
YWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFh
YWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFh
...
;
That is much bigger than max_packet_size.

This means one cannot send data to the server with mariadb-binlog --base64-output=auto | mysql ..

The task is to split BINLOG ... ;
into separate events no bigger than max_packet_size

There are two options to do that:

• Create a separate BINLOG event for each internal row_binlog_event.
• Split the BINLOG event into 'max_binlog_size' events.

Other things to fix in mariadb-binlog at the same time:

• Ensure that --base64-output=auto is default (as said in mariadb-binlog --help)
• Using --base64-output without options should be the same as using =auto