Allow zefix.settings to be overwritten by settings.php

Problem/Motivation

Currently no config values in the zefix.settings can be overwritten using a settings.php.

Steps to reproduce

Try to overwrite any 'zefix.settings' in your settings.local.php

$config['zefix.settings']['environment'] = 'production';
$config['zefix.settings']['user'] = 'testuser';
$config['zefix.settings']['password'] = 'testpass';

Proposed resolution

Use \Drupal::configFactory()->get('zefix.settings'); instead of \Drupal::configFactory()->getEditable('zefix.settings');

Remaining tasks

* Review MR

User interface changes

None

API changes

None

Data model changes

None