Improve "exists" validation with array values

* Fix return values in validation tests

* Fix exists validation with duplicate values

* Fix exists validation with duplicate database values

laravel/framework#25819

laravel/framework@144c613

src/Verifiers/EloquentPresenceVerifier.php

@@ -69,7 +69,7 @@ public function getMultiCount($collection, $column, array $values, array $extra
     {
         $query = $this->model($collection)->whereIn($column, $values);
 
-        return $this->addConditions($query, $extra)->count();
+        return $this->addConditions($query, $extra)->distinct()->count($column);
     }
 
     /**