Drop support of unsupported Symfony versions

[franmomu]

Q	A
Type	improvement
BC Break	no
Fixed issues

Summary

Ref: #2375 (comment)

I've looked for: method_exists, interface_exists, symfony 3.4 and I haven't found anything, so I guess there are no BC layers.

[IonBazan]

Initially I proposed that in #2375 but now when I think about it, ORM is supporting all versions from 3.0 to 6.0 without any maintenance overhead as Doctrine does not touch any Console nor VarDumper features that have changed recently. Since this is not a Symfony Bundle but a library, providing support for wide range of dependencies' versions is desired.

[franmomu]

I'm fine with that. Checking this, I've realised that we are not testing those versions though.

phpbench/phpbench requires symfony/console ^4.2: https://github.com/phpbench/phpbench/blob/b1ea39a7a3cf996065638fd416f3653bcb5a5aa3/composer.json#L26

symfony/cache 4.4 requires symfony/var-dump ^4.2: https://github.com/symfony/cache/blob/8810b1addbd271245af891f5ffca90a5ab5eb8f2/composer.json#L31

[IonBazan]

@franmomu should we use the vendor-bin plugin then? Or maybe try allowing super old versions of these tools like ORM did: https://github.com/doctrine/orm/blob/416aa1d2d71c8d1796781c3f57b17ba26debde26/composer.json#L41

[franmomu]

In #2375 I've removed phpbench/phpbench when executing PHPUnit tests that allows to use Symfony 6 and console 3.4