[Forwardport] Fix infinite checkout loader when some script wasn't loaded correctly because of network error

[adrian-martinez-interactiv4]

Original Pull Request

magento#14874

Description

Infinite checkout loader may appear when some module makes a require call but the dependency wasn't returned (Network error).

The patch changes how Magento treats isPending modules. If all dependencies are errored - treat it as loaded.

Manual testing scenarios

1. Open Magento/Checkout/view/frontend/web/js/model/quote.js
2. Insert the following code:

require([
    'jquery',
    'https://some-site/tracking/api/js'
], function ($) {}, function () {});

right after

define([
    'ko',
    'underscore'
], function (ko, _) {
    'use strict';

    // add code here

3. Navigate to checkout.
4. You can't purchase the product because the page is blocked by loader.

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)