Refactor TopicClient event loop

Current example for topic reader:

// Create topic client.

NYdb::NTopic::TTopicClient topicClient(driver);

// Create read session.
NYdb::NTopic::TReadSessionSettings settings;
settings
    .ConsumerName(opts.ConsumerName)
    .AppendTopics(opts.TopicPath);

ReadSession = topicClient.CreateReadSession(settings);

std::cerr << "Session was created" << std::endl;

// [BEGIN read session process events]
// Event loop
while (true) {
    auto future = ReadSession->WaitEvent();
    // Wait for next event or ten seconds
    future.Wait(TDuration::Seconds(10));
    // Get event
    std::optional<NYdb::NTopic::TReadSessionEvent::TEvent> event = ReadSession->GetEvent(true/*block - will block if no event received yet*/);
    std::cerr << "Got new read session event: " << DebugString(*event) << std::endl;

    if (auto* dataEvent = std::get_if<NYdb::NTopic::TReadSessionEvent::TDataReceivedEvent>(&*event)) {
        for (const auto& message : dataEvent->GetMessages()) {
            std::cerr << "Data message: \"" << message.GetData() << "\"" << std::endl;
        }

        if (opts.CommitAfterProcessing) {
            dataEvent->Commit();
        }
    } else if (auto* startPartitionSessionEvent = std::get_if<NYdb::NTopic::TReadSessionEvent::TStartPartitionSessionEvent>(&*event)) {
        startPartitionSessionEvent->Confirm();
    } else if (auto* stopPartitionSessionEvent = std::get_if<NYdb::NTopic::TReadSessionEvent::TStopPartitionSessionEvent>(&*event)) {
        stopPartitionSessionEvent->Confirm();
    } else if (auto* endPartitionSessionEvent = std::get_if<NYdb::NTopic::TReadSessionEvent::TEndPartitionSessionEvent>(&*event)) {
        endPartitionSessionEvent->Confirm();
    } else if (auto* closeSessionEvent = std::get_if<NYdb::NTopic::TSessionClosedEvent>(&*event)) {
        break;
    }
}

It's unfriendly API, we should design more simple and friendly API like ISimpleWriteSession

Start with the topic reader example in the issue and trace the TTopicClient, TReadSession, WaitEvent, and GetEvent entry points. Compare the requested design with the existing ISimpleWriteSession API. Done means a decided, simpler read-session event-loop API with its behavior and scope specified.