Rewrite databases rules were not considered on database assignment to
multi-threaded slave workers could break data integrity due to non
deterministic execution order.

Improved multi-threaded slave workers assignment to also consider
rewrite databases rules.

@ internal/mysql-test/suite/i_rpl/r/rpl_mts_replicate_rewrite_db.result
   Test to check that execution order is preserved on regular tables
   when MTS and replicate-rewrite-db option are used together.
@ internal/mysql-test/suite/i_rpl/t/rpl_mts_replicate_rewrite_db-slave.opt
   Test to check that execution order is preserved on regular tables
   when MTS and replicate-rewrite-db option are used together.
@ internal/mysql-test/suite/i_rpl/t/rpl_mts_replicate_rewrite_db.test
   Test to check that execution order is preserved on regular tables
   when MTS and replicate-rewrite-db option are used together.
@ internal/mysql-test/suite/i_rpl/r/rpl_mts_replicate_rewrite_db_tmp_table.result
   Test to check that execution order is preserved on temporary tables
   when MTS and replicate-rewrite-db option are used together.
@ internal/mysql-test/suite/i_rpl/t/rpl_mts_replicate_rewrite_db_tmp_table-slave.opt
   Test to check that execution order is preserved on temporary tables
   when MTS and replicate-rewrite-db option are used together.
@ internal/mysql-test/suite/i_rpl/t/rpl_mts_replicate_rewrite_db_tmp_table.test
   Test to check that execution order is preserved on temporary tables
   when MTS and replicate-rewrite-db option are used together.
@ sql/log_event.h
   Fixed database assignment to multi-threaded slave workers when rewrite
   database rules are used.
@ sql/log_event.cc
   Fixed database assignment to multi-threaded slave workers when rewrite
   database rules and temporary tables are used.
@ sql/rpl_filter.h
   Added method Rpl_filter::is_rewrite_empty().
@ sql/rpl_filter.cc
   Added method Rpl_filter::is_rewrite_empty().