Remove "previously_requested_pieces"

In #66 from a posted stacktrace
it became clear that setting previously_requested_pieces may panic.

I found a place where it was not initialized - in "on_have" callback.

I wanted to fix that + make it less error-prone, however noticed that
previously_requested_pieces isn't used at all anyway, because its use
was removed during one of the recent refactorings.

As things seem to be working fine without it, just removed it to simplify
code.

crates/librqbit/src/torrent_state/live/mod.rs

@@ -132,6 +132,10 @@ fn dummy_file() -> anyhow::Result<std::fs::File> {
         .with_context(|| format!("error opening {}", DEVNULL))
 }
 
+fn make_piece_bitfield(lengths: &Lengths) -> BF {
+    BF::from_vec(vec![0; lengths.piece_bitfield_bytes()])
+}
+
 pub(crate) struct TorrentStateLocked {
     // What chunks we have and need.
     // If this is None, the torrent was paused, and this live state is useless, and needs to be dropped.
@@ -429,10 +433,7 @@ impl TorrentStateLive {
             addr: checked_peer.addr,
             on_bitfield_notify: Default::default(),
             unchoke_notify: Default::default(),
-            locked: RwLock::new(PeerHandlerLocked {
-                i_am_choked: true,
-                previously_requested_pieces: BF::new(),
-            }),
+            locked: RwLock::new(PeerHandlerLocked { i_am_choked: true }),
             requests_sem: Semaphore::new(0),
             state: self.clone(),
             tx,
@@ -493,10 +494,7 @@ impl TorrentStateLive {
             addr,
             on_bitfield_notify: Default::default(),
             unchoke_notify: Default::default(),
-            locked: RwLock::new(PeerHandlerLocked {
-                i_am_choked: true,
-                previously_requested_pieces: BF::new(),
-            }),
+            locked: RwLock::new(PeerHandlerLocked { i_am_choked: true }),
             requests_sem: Semaphore::new(0),
             state: state.clone(),
             tx,
@@ -780,10 +778,6 @@ impl TorrentStateLive {
 
 struct PeerHandlerLocked {
     pub i_am_choked: bool,
-
-    // This is used to only request a piece from a peer once when stealing from others.
-    // So that you don't steal then re-steal the same piece in a loop.
-    pub previously_requested_pieces: BF,
 }
 
 // All peer state that would never be used by other actors should pe put here.
@@ -1117,8 +1111,7 @@ impl PeerHandler {
                 // If bitfield wasn't allocated yet, let's do it. Some clients start empty so they never
                 // send bitfields.
                 if live.bitfield.is_empty() {
-                    live.bitfield =
-                        BF::from_vec(vec![0; self.state.lengths.piece_bitfield_bytes()]);
+                    live.bitfield = make_piece_bitfield(&self.state.lengths);
                 }
                 match live.bitfield.get_mut(have as usize) {
                     Some(mut v) => *v = true,
@@ -1128,8 +1121,8 @@ impl PeerHandler {
                     }
                 };
                 trace!("updated bitfield with have={}", have);
-                self.on_bitfield_notify.notify_waiters();
             });
+        self.on_bitfield_notify.notify_waiters();
     }
 
     fn on_bitfield(&self, bitfield: ByteString) -> anyhow::Result<()> {
@@ -1140,7 +1133,6 @@ impl PeerHandler {
                 self.state.lengths.piece_bitfield_bytes(),
             );
         }
-        self.locked.write().previously_requested_pieces = BF::from_vec(vec![0; bitfield.len()]);
         self.state
             .peers
             .update_bitfield_from_vec(self.addr, bitfield.0);
@@ -1229,11 +1221,6 @@ impl PeerHandler {
                 }
             };
 
-            self.locked
-                .write()
-                .previously_requested_pieces
-                .set(next.get() as usize, true);
-
             for chunk in self.state.lengths.iter_chunk_infos(next) {
                 let request = Request {
                     index: next.get(),