[Forwardport] Remove PDF files after generation

[tiagosampaio]

Original Pull Request

#16401

Description

Upon invoice/packingslip/credit memo printing the system generates a PDF file directly in the var directory. I see no reason for keeping these files since they are not accessible publicly via web (sharing purpose). There's no "reuse" purpose as well since on every print action a new file with a new filename is being generated.
This PR provides a logic for removing a PDF file once it's generated.
Currently, it's implemented only within a scope of the invoice printing. Once we agree on the solution, I will adjust other places with PDF generation.

Fixed Issues (if relevant)

1. Print pdf don't delete file in var folder #3535
2. PDF invoices in /var folder #14517

Manual testing scenarios

• Open an existing invoice in the admin panel.
• Click the "Print" button.
• You should have the invoice downloaded.
• You should not have a generated PDF file in the var directory.

[magento-engcom-team]

Hi @tiagosampaio. 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:

• @magento-engcom-team give me test instance - deploy test instance based on PR changes
• @magento-engcom-team give me {$VERSION} instance - deploy vanilla Magento instance

For more details, please, review the Magento Contributor Assistant documentation

[miguelbalparda]

@tiagosampaio I've seen you routinely port other devs code. I'd rather have the original author doing the back/forward port when possible and you porting everything that's available is not helping with that.

[tiagosampaio]

@miguelbalparda as you wish, Sr.

[magento-engcom-team]

Hi @tiagosampaio. 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.