Fix Inconsistent DHT

[rishiad]

This PR addresses the issue where larger files took an extended time to have all their pieces inserted into the Distributed Hash Table (DHT). The solution involves the following changes:

1. DHT Insertion Timing: The DHT insertion process has been moved to the piece processing stage, which improves efficiency.
2. Tagging Process: Tagging is now handled by the worker threads. This change ensures that only the validator who has tagged the pieces can send the challenge, making it redundant to publish the tags in the DHT.
3. Local Tag Table: Instead of relying on the DHT for tags, we now maintain a local table of tags.

closes #41