[Validator] Add shortcut to create a new ConstraintViolationList with one Constraint

[lyrixx]

Description It's very common to do that in Symfony Application:

$violations = new ConstraintViolationList();
$violations->add(new ConstraintViolation('A publish is already running.', '', [], null, '', null));

// use ApiPlatform\Core\Bridge\Symfony\Validator\Exception\ValidationException;
throw new ValidationException($violations);

Note: The last line is not related, but will help to better undertand

As you can see, it's a bit boring and really not straightforward to create this piece of code E_TOO_MANY_PARAMETER

What do you thing about something like:

$violations = ConstraintViolationList::createSingleConstraint('A publish is already running.');

throw new ValidationException($violations);

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If it's OK for you, I'll do the PR

[ro0NL]

IMHO createSingleConstraint('...') implies the same as new ConstraintViolation('...'), and then new ConstraintViolationList([new ConstraintViolation('..')]) isnt that bad.

To utilize that, i suggest ConstraintViolationList::createFromMessage(s)