Change backup column in database to LONGTEXT to support sites with many permissions

Patch works, I tested personally on our live site (because we have lots of roles and many permissions) and it'd bug out because the payload was too big for the database column.

I'm running Drupal 9, the latest. Good work @natefollmer !

I would recommend adding the following to the backup_permissions.install file, just
so that way if someone uninstalls the module then it'll drop the backup_permissions table.

/**
 * hook_uninstall
 * deletes schema upon module uninstall
 */
function backup_permissions_uninstall(){
    drupal_uninstall_schema('backup_permissions');
}