[Forwardport] magento/magento2#4389 Widget cache error

[ihor-sviziev]

Original Pull Request

#12764

• fixed CacheKey assignment

Description

Fixed Issues (if relevant)

1. Widget cache error #4389: Widget cache error

Manual testing scenarios

1. Install Magento from develop branch.
2. Add two widgets of type 'Catalog Product List' to the 'CMS homepage' at location content.bottom with different titles, but the same conditions. For example, condition could be product price is greater than 0
3. Refresh cache and visit homepage

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 @ihor-sviziev. Thank you for your contribution.
Changes from your Pull Request will be available with the upcoming 2.3.0 release.