[Forwardport] Improve array output format for etc.php and config.php

[namlier]

Original pull request

#14042

Description

This improved the syntax of the generated files app/etc/env.php and app/etc/config.php by using 4 instead of 2 spaces and by removing whitelines after "=>".

Fixed Issues (if relevant)

The generated array code wasn't compliant to formatting standard. Example from config.php:

<?php
return [
  'modules' => 
  [
    'Magento_Store' => 1,
    'Magento_AdvancedPricingImportExport' => 1,

Manual testing scenarios

1. Run a command which regenerates env.php and/or config.php, i.e. bin/magento config:set general/store_information/name "My Store" --lock-config
2. Check that the generated file (i.e. app/etc/config.php) is formatted like this, with 4 space indent and removed line breaks:

<?php
return [
    'modules' => [
        'Magento_Store' => 1,
        'Magento_AdvancedPricingImportExport' => 1,

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)