Fix blob binding overwrite on DB2

On DB2 when binding more than 1 blob in the same statement each subsequent blob overwrites previous one.
So instead of [1, 2, 3] we get [2, 3, 3]
This happens because of reference between loop variable `$value` and the item in `$this->parameters[]`,
which remains after iteration, see `bindLobs` and `bind` methods in `\Doctrine\DBAL\Driver\IBMDB2\Statement`

src/Driver/IBMDB2/Statement.php

@@ -182,6 +182,8 @@ private function bindLobs(): array
             } else {
                 $this->bind($param, $value, DB2_PARAM_IN, DB2_CHAR);
             }
+
+            unset($value);
         }
 
         return $handles;

tests/Functional/Driver/IBMDB2/StatementTest.php

@@ -5,6 +5,7 @@
 namespace Doctrine\DBAL\Tests\Functional\Driver\IBMDB2;
 
 use Doctrine\DBAL\Driver\IBMDB2\Exception\StatementError;
+use Doctrine\DBAL\ParameterType;
 use Doctrine\DBAL\Tests\FunctionalTestCase;
 use Doctrine\DBAL\Tests\TestUtil;
 
@@ -36,4 +37,16 @@ public function testExecutionErrorsAreNotSuppressed(): void
         $this->expectException(StatementError::class);
         $stmt->execute([[]]);
     }
+
+    public function testBlobBindingDoesNotOverwritePrevious(): void
+    {
+        $params = ['test1', 'test2'];
+        $values = $this->connection->fetchNumeric(
+            'SELECT CAST(? AS VARCHAR) AS a, CAST(? AS VARCHAR) AS b FROM SYSIBM.SYSDUMMY1',
+            $params,
+            [ParameterType::LARGE_OBJECT, ParameterType::LARGE_OBJECT],
+        );
+
+        self::assertEquals(['test1', 'test2'], $values);
+    }
 }