* PT-1897 pt-stalk on MySQL 8 not collecting lock information
For version prior 8.0 pt-stalk continue using Information Schema INNODB_LOCKS and INNODB_LOCK_WAITS tables for collecting lock information.
For version 8.0 and higher pt-stalk uses tables data_locks and data_lock_waits in Performance Schema
* PT-1897 - Better MariaDB support
We cannot simply compare version number with 8.0 to identify if lock tables are in Performance Schema,
because MariaDB 10.x still have them in the Information Schema.
Therefore added additional flag, indicating which syntax we should use
* Tests for PT-1897
* PT-1897: added missed samples for tests
* PT-1897 Fixed retention test
Co-authored-by: Carlos Salguero <carlos.salguero@percona.com>
