[composer-based] Bond AddViolationToBuildViolationRector to symfony/validator 2.5

[TomasVotruba]

AddViolationToBuildViolationRector rewrites ExecutionContextInterface::addViolationAt() into the buildViolation() fluent builder:

-$this->context->addViolationAt('property', 'The value {{ value }} is invalid.', [
-    '{{ value }}' => $value,
-]);
+$this->context->buildViolation('The value {{ value }} is invalid.')
+    ->atPath('property')
+    ->setParameter('{{ value }}', $value)
+    ->addViolation();

That builder arrived in the validator component in 2.5, so the rule can declare the constraint itself:

public function provideComposerPackageConstraint(): ComposerPackageConstraint
{
    return new ComposerPackageConstraint('symfony/validator', '>=2.5');
}

and be registered once in the composer-based set, instead of relying on the Symfony 2.5 version set to be picked up on a direct upgrade from an older version.

symfony/validator, not symfony/symfony — a project installing the split components, which is nearly all of them today, carries no symfony/symfony to match against. Same package the neighbouring ValidatorBuilderEnableAnnotationMappingRector binds to.

A fixture in tests/ComposerBased/Fixture/ covers it through the set itself, so the rule being dropped from the list would fail a test rather than pass quietly.