PHP 7.4 support

### Description (*)

- add PHP 7.4 compatibility
- remove 7.1 and 7.2 compatibility
- keep 7.3 compatibility
- make code and tests comply with this change
- tests should be compatible with PHPUnit 9



Default branch:  https://github.com/magento/security-package/tree/1.0-develop
- Google reCAPCTHA
- Security.txt