fix(fleet,mysql): switch Fleet to MariaDB, add mysql case to manage_tool_repository

- fleet: use setup_mariadb instead of setup_mysql (MariaDB works fine for
  Fleet and avoids MySQL repo complexity on trixie)
- tools.func: add missing mysql) case block to manage_tool_repository
  (was causing 'Unknown tool repository: mysql' error)

install/fleet-install.sh

@@ -13,7 +13,7 @@ setting_up_container
 network_check
 update_os
 
-setup_mysql
+setup_mariadb
 
 msg_info "Setting up Database"
 FLEET_DB_PASS=$(openssl rand -base64 18 | tr -dc 'a-zA-Z0-9' | head -c 13)