doctrine#11977 only perform batching if/when the AssignedGenerator is in use

The `SequenceGenerator` is potentially used for PostgreSQL table auto-generated fields, but
the `SequenceGenerator` is not a **POST**-insert generator.

Because the `SequenceGenerator` is used in the middle of `INSERT` operations performed
by persisters, we cannot rely on it in batching operations: disabling it, so we get a green
test suite on PostgreSQL.

This change makes `GH10531Test` pass on PostgreSQL: see doctrine#10531

Author: Ocramius

src/Internal/UnitOfWork/InsertBatch.php

@@ -5,6 +5,7 @@
 namespace Doctrine\ORM\Internal\UnitOfWork;
 
 use Doctrine\ORM\EntityManagerInterface;
+use Doctrine\ORM\Id\AssignedGenerator;
 use Doctrine\ORM\Mapping\ClassMetadata;
 
 /**
@@ -55,7 +56,7 @@ public static function batchByEntityType(
 
             if (
                 $currentClass?->name !== $entityClass->name
-                || $entityClass->idGenerator->isPostInsertGenerator()
+                || ! $entityClass->idGenerator instanceof AssignedGenerator
             ) {
                 $currentClass = $entityClass;
                 $batches[]    = new InsertBatch($entityClass, [$entity]);