Cleanup and PHP 7.2 Support

[buskamuza]

To simplify current work and future maintenance of ZF1, investigate possibility of removal of ZF1 components that are not used in Magento 2 (2.3-develop).
As a next possible step, investigate efforts necessary to update remaining components.
And for all components that can't be either removed or updated, investigate efforts necessary to support PHP 7.2.

AC:

• list of components that can be safely removed
• list of components that can be easily upgraded to ZF 2/3
  • include details of the necessary effort
• list of components that should be fixed to support PHP 7.2
  • include details of the necessary effort

[dmanners]

I know from experience that:

Zend_Captcha could be removed as it has already been updated to the ZF2 version. magento/magento2#8356 I am not sure if that could also be updated to the latest version also.

Zend_Json cannot sadly be removed as yet though it is only used in https://github.com/magento/magento2/blob/2.3-develop/lib/internal/Magento/Framework/Json/Decoder.php and https://github.com/magento/magento2/blob/2.3-develop/lib/internal/Magento/Framework/Json/Encoder.php which are both deprecated. We would have to update the usage of these classes as well as https://github.com/magento/magento2/blob/2.3-develop/lib/internal/Magento/Framework/Json/Helper/Data.php before we could remove Zend_Json

[buskamuza]

Thanks, @dmanners .

I think we should be able to remove all deprecated Json functionality in 2.3. This means we can remove Zend_Json.