refactor: [torrust#1495] add SwarmMetadata to Swarm

- Moved responsability for keeping metadata to the Swarm type.
- Number of seeder and leechers is now calculated when the Swarm changes
  not on-demand. We avoid iterating over the peers to get the number of
seeders and leechers.
- The number of downloads is also calculate now in the Swarm. It will be
  removed from the TrackedTorrent.

Author: josecelano

packages/primitives/src/swarm_metadata.rs

@@ -7,7 +7,7 @@ use derive_more::Constructor;
 /// Swarm metadata dictionary in the scrape response.
 ///
 /// See [BEP 48: Tracker Protocol Extension: Scrape](https://www.bittorrent.org/beps/bep_0048.html)
-#[derive(Copy, Clone, Debug, PartialEq, Default, Constructor)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Default, Constructor)]
 pub struct SwarmMetadata {
     /// (i.e `completed`): The number of peers that have ever completed
     /// downloading a given torrent.
@@ -27,6 +27,21 @@ impl SwarmMetadata {
     pub fn zeroed() -> Self {
         Self::default()
     }
+
+    #[must_use]
+    pub fn downloads(&self) -> u32 {
+        self.downloaded
+    }
+
+    #[must_use]
+    pub fn seeders(&self) -> u32 {
+        self.complete
+    }
+
+    #[must_use]
+    pub fn leechers(&self) -> u32 {
+        self.incomplete
+    }
 }
 
 /// Structure that holds aggregate swarm metadata.