Make polling required

[klimick]

Current consumer behaviour with listenForInserts: true gives the impression that polling is no longer required.
Actually, consumer may get stuck and not process messages that are already in the queue.

/** @var PostgresConnectionPool $pg */

$queue = createQueue($pg, 'test_queue');
$queue->send(new SendMessage(valueJson: '"begin"'));
$queue->send(new SendMessage(valueJson: '"stop"'));

$config = new ConsumeConfig(
    queue: $queue->name,
    batch: 1,
    pollInterval: TimeSpan::fromSeconds(0),
    listenForInserts: true,
);

$consumer = createConsumer($pg);

// Due to `batch: 1`, only the "begin" message will be consumed.
// The "stop" message will remain in the queue until a new INSERT occurs
// or the consumer is restarted.
$ctx = $consumer->consume(
    handler: static function (array $messages, ConsumeController $ctx) {
        foreach ($messages as $message) {
            if ($message->value === '"stop"') {
                $ctx->stop();
            }
        }

        $ctx->ack($messages);
    },
    config: $config,
);

$ctx->awaitCompletion();