Extend TopicConfiguration to support dynamic configuration when creating topics

[shlomiassaf]

Description

Dynamic values are valid input when creating a topic.

The PR will allow adding them, so for example, one can provide the retention period and cleanup policy of the topic:

         clusterManager.CreateIfNotExistsAsync("mytopic", 1, 1, new Dictionary<string, string>
          {
              { "retention.ms", (86400000 * 2).ToString() }, // 2 days
              { "cleanup.policy", "delete" }
          });

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have added tests to cover my changes
• I have made corresponding changes to the documentation

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