Fix Serializer encode for NonSendableStampInterface about messenger HOT 1 OPEN

readonly class FooInterchangeableSerializer implements SerializerInterface
{
    public function encode(Envelope $envelope): array
    {
        $envelope = $envelope->withoutStampsOfType(NonSendableStampInterface::class);

        [...]
     }
     
     public function decode(array $encodedEnvelope): Envelope
    {
        if (empty($encodedEnvelope['body'])) {
            throw new MessageDecodingFailedException('Encoded envelope should have at least a "body".');
        }

        $headers = $encodedEnvelope['headers'];
        $stamps = [];
        if (isset($headers['stamps'])) {
            /** @var array $stamps */
            $stamps = unserialize(base64_decode($headers['stamps']));
        }

        /**
         * The method all() returns a different format that the one excepted by the {@see Envelope::__construct()},
         * so normalize them.
         */
        /** @var StampInterface[] $normalizedStamps */
        $normalizedStamps = [];
        foreach ($stamps as $stamp) {
            if (!is_array($stamp)) {
                $normalizedStamps[] = $stamp;
                continue;
            }

            foreach ($stamp as $innerStamp) {
                $normalizedStamps[] = $innerStamp;
            }
        }

        $body = $encodedEnvelope['body'];
        $event = EventSerializer::decode($body);

        return new Envelope($event, $normalizedStamps);
    }
}