Support making config suite optional

[mariacha]

Based on the work in thinkshout/robo-drupal#73 and this Pr: https://github.com/thinkshout/lvhn/pull/5208/files

Dev work:

• Update this repo to make config-suite its own configuration option immediately on fresh install
• Add this to settings.dev.php as a commented-out optional config:

// Uncomment if you don't want to use config_suite's auto-export configuration behavior:
// $config['config_split.config_split.config_live']['status'] = FALSE;

Documentation/change management

• Document how existing sites could update to not get the dirty robo install folders.
• Document how developers can overwrite the option to even use config-suite, if they don't want to use it.
  $config['config_split.config_split.config_suite_only']['status'] = FALSE; -- figure out where to note this.