This patch added transaction length information to the Gtid_log_event in the
binary log.

The new information is calculated before writing the Gtid_log_event to
the binary log, by consulting the binary log cache length, the amount of
events present the cache, the Gtid_log_event length and checksumming
flag on the cache.

trx_length = cache_length + gtid_length +
             cache_checksum_active * (cache_events + 1 ) * CRC32_payload

Where cache_checksum_active is 1 when binary log checksumming is ON and
0 otherwise.

Code changes
------------

@libbinlogevents/*/control_events.{h|cpp}:

Introduced the transaction_length parameter into Gtid_event.

@rapid/plugin/group_replication/src/handlers/certification_handler.cc:

Set the transaction_length for a copy of a Gtid_log_event.

@rapid/plugin/group_replication/src/observer_trans.cc:

Set the transaction_length for a transaction to be certified.

@sql/binlog.cc:

Introduced the infrastructure to count the amount of events present in a
binary log cache.

Introduced a function to state if checksum is enable for the binary log
cache.

MYSQL_BIN_LOG::write_gtid() now calculates and store the transaction
length before writing the Gtid_log_event into the binary log.

@sql/log_event.{h|cc}:

Updated Gtid_log_event functions to dump event information (used by
mysqlbinlog client program) and to write the transaction_length in
Gtid_log_event::write_body_to_memory().

Created Gtid_log_event::set_trx_length_by_cache_size() function to
calculate and set the transaction length based on binlog cache info.

The mysqlbinlog client program will print "transaction_length=" followed
by the transaction length information on the Gtid_log_event or 0 when
the information is not available.

Updated Gtid_log_event::get_data_size() to take into account the
transaction_length field.

Introduced Gtid_log_event::get_event_length() to answer with the
Gtid_log_event length (including event header, but not CRC32).

MTR include changes
-------------------

@include/assert_transaction_length.inc:

Assert all transaction lengths for a given binary/relay log file.

@include/assert_transaction_length_all_logs.inc:

Assert all transaction lengths for all server binary and relay log
files.

@include/mysqlbinlog.inc:

Mask the transaction length output.

@include/rpl_end.inc:

Now supporting the optional '$rpl_assert_transaction_length' parameter.
When set to 1, the include will call, without displaying output,
assert_transaction_length_all_logs.inc for all servers on the test case.

New test case
-------------

@rpl.rpl_transaction_size

Generate some random workload and assert all transactions length.

Test cases changed or needed to be recorded again
-------------------------------------------------

The test cases below source "include/mysqlbinlog.inc" or dump
mysqlbinlog output that required masking the transaction length field:

@binlog_gtid.binlog_gtid_mysqlbinlog_row
@binlog_gtid.binlog_gtid_mysqlbinlog_row_innodb
@binlog_gtid.binlog_gtid_mysqlbinlog_row_myisam
@binlog_nogtid.binlog_mysqlbinlog_row
@binlog_nogtid.binlog_mysqlbinlog_row_innodb
@binlog_nogtid.binlog_mysqlbinlog_row_myisam
@binlog_nogtid.binlog_mysqlbinlog_row_trans
@rpl.rpl_multi_source_corrupt_repository
@rpl_nogtid.rpl_binlog_json
@rpl_nogtid.rpl_row_ignorable_event
@group_replication.gr_foreign_key_on_unique_key
@group_replication.gr_parallel_applier_indexes
@group_replication.gr_parallel_applier_sequential_indexes