Introduce sql_require_primary_key

MySQL 8 introduced sql_require_primary_key.

Similar option (global option, affecting all Engines, unlike innodb_force_primary_key) should be available on MariaDB too.

MariaDB 10.1 introduced the innodb_force_primary_key variable, which forces InnoDB tables to have a primary key. Unfortunately, this doesn’t solve the replication problem if we use other storage engines.

sql_require_primary_key from MySQL8 simply disallows to create tables without a primary key, or drop a primary key from an existing table.

https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_sql_require_primary_key