find out which transactions can be safely executed concurrently on the
slave. The transactions are tracked on the master and the binary log
commit_parent field, which is used by the MTS applier on the slave, is
changed to consider writeset dependencies between transactions.

Relevant changes to the code:
 - introduces two new options: binlog-transaction-dependency-tracking,
   which selects the tracking mode between COMMIT_ORDER, WRITESET and
   WRITESET_SESSION, and binlog-transaction-dependency-history-size.
 - adds the Transaction_dependency_tracker and associated classes
   Commit_order_trx_dependency_tracker, Writeset_trx_dependency_tracker
   and Writeset_session_trx_dependency_tracker, specific to each of the
   tracking modes (in the new rpl_trx_tracking.h/.cc files).
 - to support the WRITESET mode, the hashes of each row touched by a
   transaction are stored in the m_writeset_history map, up to the size
   determined by the binlog-transaction-dependency-history-size option.
 - to support the WRITESET_SESSION mode, the Dependency_tracker_ctx is
   added to the THD so that the last sequence_number used by a client is
   available for future transactions of the same session.
 - extends the function add_pke to track transactions that touch tables
   with primary keys and tables without them, so that partial writesets
   are detected.

This WL back-ports WL#9556 to MySQL 5.7, in addition to the fixes for
the following bugs:
BUG#25950554: THE FUNCTION RESET_CONNECTION DOES NOT RESET WRITE SET...
BUG#25982097: WRITESET DEPENDENCY TRACKING SUB-OPTIMAL AFTER ROTATION...