refactor!: Move ConnectionId and PendingPoint to libp2p-swarm (#3346)

Both of these are only needed as part of `libp2p-swarm`. Them residing in `libp2p-core` is a left-over from when `libp2p-core` still contained `Pool`.

swarm/src/connection.rs

@@ -42,13 +42,36 @@ use libp2p_core::connection::ConnectedPoint;
 use libp2p_core::multiaddr::Multiaddr;
 use libp2p_core::muxing::{StreamMuxerBox, StreamMuxerEvent, StreamMuxerExt, SubstreamBox};
 use libp2p_core::upgrade::{InboundUpgradeApply, OutboundUpgradeApply};
-use libp2p_core::PeerId;
 use libp2p_core::{upgrade, UpgradeError};
+use libp2p_core::{Endpoint, PeerId};
 use std::future::Future;
 use std::task::Waker;
 use std::time::Duration;
 use std::{fmt, io, mem, pin::Pin, task::Context, task::Poll};
 
+/// Connection identifier.
+#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
+pub struct ConnectionId(usize);
+
+impl ConnectionId {
+    /// Creates a `ConnectionId` from a non-negative integer.
+    ///
+    /// This is primarily useful for creating connection IDs
+    /// in test environments. There is in general no guarantee
+    /// that all connection IDs are based on non-negative integers.
+    pub fn new(id: usize) -> Self {
+        Self(id)
+    }
+}
+
+impl std::ops::Add<usize> for ConnectionId {
+    type Output = Self;
+
+    fn add(self, other: usize) -> Self {
+        Self(self.0 + other)
+    }
+}
+
 /// Information about a successfully established connection.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Connected {
@@ -824,3 +847,39 @@ mod tests {
         }
     }
 }
+
+/// The endpoint roles associated with a pending peer-to-peer connection.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+enum PendingPoint {
+    /// The socket comes from a dialer.
+    ///
+    /// There is no single address associated with the Dialer of a pending
+    /// connection. Addresses are dialed in parallel. Only once the first dial
+    /// is successful is the address of the connection known.
+    Dialer {
+        /// Same as [`ConnectedPoint::Dialer`] `role_override`.
+        role_override: Endpoint,
+    },
+    /// The socket comes from a listener.
+    Listener {
+        /// Local connection address.
+        local_addr: Multiaddr,
+        /// Address used to send back data to the remote.
+        send_back_addr: Multiaddr,
+    },
+}
+
+impl From<ConnectedPoint> for PendingPoint {
+    fn from(endpoint: ConnectedPoint) -> Self {
+        match endpoint {
+            ConnectedPoint::Dialer { role_override, .. } => PendingPoint::Dialer { role_override },
+            ConnectedPoint::Listener {
+                local_addr,
+                send_back_addr,
+            } => PendingPoint::Listener {
+                local_addr,
+                send_back_addr,
+            },
+        }
+    }
+}