[Forwardport] Fix Missing meta title tag and doesn't show product name if meta title is empty

[nmalevanec]

Original Pull Request

#15532

Description

The current Magento behaviour does not allow to specify a title meta tag and the "Meta Title" option in the product's page is binded to the page's title.

This PR adds the meta tile tag and allows to use title and meta title independently.

Fixed Issues (if relevant)

1. M2.2.4 missing meta title tag and doesn't show product name if meta title is empty #15501: M2.2.4 missing meta title tag and doesn't show product name if meta title is empty

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 @nmalevanec. Thank you for your contribution
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[sidolov]

Hi @nmalevanec , why you skipped code fragment in ``processMetadataContent` method from original PR? Looks like this changes should be ported too

[nmalevanec]

@sidolov, because 'processMetadataContent' in 2.3-develop seems more flexible and basically 'processMetadataContent' from original pr doesn't work because doesn't considering 'title' case.

 if ($name === 'title') {
            if (!$content) {
                $content = $this->escaper->escapeHtml($this->pageConfig->$method()->get());
            }
            return $content;
        }

[magento-engcom-team]

Hi @sidolov, thank you for the review.
ENGCOM-2874 has been created to process this Pull Request

[magento-engcom-team]

Hi @nmalevanec. Thank you for your contribution.
We will aim to release these changes as part of 2.3.0.
Please check the release notes for final confirmation.