Relates to:

• Extract duplicate implementation of InfoHash struct torrust-index#251
• Refactor packages #753

We are duplicating code for:

pub struct InfoHash(pub [u8; 20]);

• https://github.com/torrust/torrust-tracker/blob/develop/src/shared/bit_torrent/info_hash.rs#L136-L167
• https://github.com/torrust/torrust-index-backend/blob/develop/src/models/info_hash.rs#L136-L167

We should extract a common BitTorrent protocol crate for both the Tracker and the Index Backend.