topic manager wait

[frairon]

This PR adds a simple polling mechanism for the TopicManager after creating a topic to be fully populated in the cluster.

[paulhenke]

Another approach

// or better get ctx passed as param in waitForCreated instead of using .Background()
ctx, cancel := context.WithTimeout(context.Background, m.topicManagerConfig.CreateTopicTimeout)
defer cancel()

for ctx.Err() == nil {
	_, err := m.Partitions(topic)
	switch err {
	case nil: 
		return nil
	case errTopicNotFound:
		time.Sleep(time.Second)
	default: 
		return fmt.Errorf("error checking topic: %w", err)
	}
}

[frairon]

I was thinking of adding the context as a param, but that would mean changing the whole api.
But the timeout context is definitely an improvement, didn't think of this. so Thanks :)

[frairon]

@paulhenke fixed.