Using numerics any reference name causes error with v1.8.1

[mssimi]

Bug Report

Q	A
Version	1.8.1

Summary

After upgrade from 1.7.0 to 1.8.1 reference name that is numeric does not work, even when it is typed string.

Current behavior

Using numeric reference name causes error with 1.8.1, but not with 1.7.0

Expected behavior

Using numeric reference name working for both 1.7.0 and 1.8.1

How to reproduce

With 1.8.1

$this->setReference('a12345', $anyEntity); // works
$this->setReference('12345', $anyEntity); // throws error 

 Doctrine\Common\DataFixtures\ReferenceRepository::setReferenceIdentity(): A  
  rgument #1 ($name) must be of type string, int given, called in /srv/vendor  
  /doctrine/data-fixtures/src/Event/Listener/ORMReferenceListener.php on line  
   52                       

With 1.7.0

$this->setReference('a12345', $anyEntity); // works
$this->setReference('12345', $anyEntity); // works too

[ovitores]

Hi!...

This fails because now the method ReferenceRepository::setReferenceIdentity(string $name, mixed $identity, string $class): void typed the parameter $name with string type, and numeric reference names is casted to integers when are recovered from ReferenceRepository::getReferenceNames($object) method in previous lines, so when pass the value of numeric name in integer with a parameter typed with string then fails.

So I propose a fix to cast names to string in ReferenceRepository::getReferenceNames($object) when are returned