Improvevariablesdocumentation

Partially fixes : #14143

From what I tested almost all existing variables have documentation when using this code.

• Uses preferential mode MySQL docs for MySQL users and MariaDB docs for MariaDB users


• Unit tests now use data that only exists for tests


• Added package williamdes/mariadb-mysql-kbs

Original commits :
- https://github.com/williamdes/phpmyadmintest/tree/docsv1
- https://github.com/williamdes/phpmyadmintest/commit/2d6cc8d2c7285dbe45add9f2124ba90a4f8b0dcc
- https://github.com/williamdes/phpmyadmintest/commit/c80e1b2c0f5e3787c2ac90f7d61a706948bbc95a
- https://github.com/williamdes/phpmyadmintest/commit/5753281fa33e056968f8a4d7a62c9db854774b97
- https://github.com/williamdes/phpmyadmintest/commit/6ebf7739d9758d558ded996cb32ee843b20c6525

该提问来源于开源项目：phpmyadmin/phpmyadmin