Drop Symfony 4.4 and Twig 2

[jordisala1991]

Subject

I am targeting this branch, because this is BC.

Changelog

### Removed
- Support for Symfony 4.4
- Support for Twig 2

[jordisala1991]

I have added more database versions to test (more postgres and mysql versions). Modified php version for those tests too.

[VincentLanglet]

There is still tags for twig 2 https://github.com/twigphp/Twig/tags, is it really abandonned ?

[jordisala1991]

We are dropping it on next majors anyway, why not do it right away? https://packagist.org/packages/twig/twig#v3.0.0 twig 3 is more than 3 years old...

[VincentLanglet]

We are dropping it on next majors anyway, why not do it right away? packagist.org/packages/twig/twig#v3.0.0 twig 3 is more than 3 years old...

I just dont know this package enough to know if there was a reason for twig to not abandon the v2. Maybe some people are stuck with v2 for some weird reason...