[Forwardport] Making configurable settings for MAX_IMAGE_WIDTH and MAX_IMAGE_HEIGHT

[nmalevanec]

Original Pull Request

#15942

Description

It was added a new system fieldset, where the max-width and max-height can be set.
Stores / Configuration / Advanced / System / Images Configuration

So these 2 values are more flexible now for those which need to have bigger images in their shops.

Fixed Issues (if relevant)

1. Wysiwyg > Image Uploader >Max width/height #13747: Wysiwyg > Image Uploader >Max width/height
2. ...

Manual testing scenarios

1. Get an image of 3000x700
   https://dummyimage.com/3000x700
2. Open any wysiwyg editor
3. Upload an image
4. The uploaded image should have maximum configured size

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
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 @sidolov, thank you for the review.
ENGCOM-2955 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.