[Form] solved dependency to ValidatorInterface, fix #11036

| Q             | A
| ------------- | ---
| Bug fix?      | [yes]
| New feature?  | [no]
| BC breaks?    | [no]
| Deprecations? | [no]
| Tests pass?   | [yes]
| Fixed tickets | #11036, #11345
| License       | MIT
| Doc PR        | 

Since Symfony 2.5

The problem was that the form component has a hardcoded decency to the deprecated validator component.
The pull request fixes the dependency to the validator component and supports now both implementations.

@Symfony Core Members
please review the changes https://github.com/sebastianblum/symfony/blob/0a1e9c208f8730219bebf89f6696b246a0c88da7/src/Symfony/Component/Form/Extension/Validator/ValidatorExtension.php
I'm not sure if it was the right solution

I would remove this ``@throws`` actually. It is not an exception you would want to catch (I even think we could use the SPL exception directly here). the only reason why we throw an exception is because PHP does not allow to have 2 typehinted signatures for the constructor