wp core config is deprecated

The command wp core config have to be changed by wp config.

https://github.com/wp-cli/wp-cli/issues/3728

https://developer.wordpress.org/cli/commands/config/

So wp core config becomes wp config creates to create the first wp-config.php file.

New commands are available :

• wp config get.
• wp config has.
• wp config set.

So, instead of using file_line resource, we can use exec with this new set of commands to manage the wp-config.php file.