Fixed configurable product widget issue

[gelanivishal]

Description (*)

Fixed issue configurable products in widgets.

Fixed Issues (if relevant)

1. Issue with configurable products in widgets, not added to cart #19315: Issue with configurable products in widgets, not added to cart

Manual testing scenarios (*)

1. Create a product attribute, for example Size with several values (S, M and L). This attribute must have property "use in product listing" set to Yes.
2. Create a product that uses this attribute with a configuration setting. Define different quantities for each values. Set this product as new for the current month.
3. Create a block with a widget for new products (choose the grid template) and add this block at any page.
4. On this page click on Add to cart for this new product.

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)

[magento-engcom-team]

Hi @gelanivishal. Thank you for your contribution
Here is some useful tips how you can test your changes using Magento test environment.
Add the comment under your pull request to deploy test or vanilla Magento instance:

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[magento-engcom-team]

Hi @sivaschenko, thank you for the review.
ENGCOM-3516 has been created to process this Pull Request

[jcourtei]

In new_default_list.phtml it should be $_product instead of $_item

[gelanivishal]

@jcourtei I have updated it.

[jcourtei]

@gelanivishal Thanks!

[magento-engcom-team]

Hi @gelanivishal. Thank you for your contribution.
We will aim to release these changes as part of 2.3.1.
Please check the release notes for final confirmation.