refactor: replace channel with callback of transport in swarm

[Ma233]

Please check if the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes/features)
• Docs have been added / updated (for bug fixes / features)

🔵 What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

🟤 What is the current behavior? (You can also link to an open issue here)

🟢 What is the new behavior (if this is a feature change)?

☢️ Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)

ℹ️ Other information

Closes #issue

[RyanKung]

plz avoid exposing swarm components such as:

➜  core git:(ma_channel) ✗ pcregrep -rM 'swarm.transport(\n)?.*' src
src/swarm/builder.rs:    /// Sets up the external address for swarm transport.
src/dht/stabilization.rs:        let conns = self.swarm.transport.get_connections();
src/dht/stabilization.rs:                    self.swarm.transport.session_sk(),
src/dht/stabilization.rs:                self.swarm.transport.send_payload(payload).await?;
src/dht/stabilization.rs:                        self.swarm.transport.session_sk(),
src/dht/stabilization.rs:                    self.swarm.transport.send_payload(payload).await?;
src/tests/default/test_connection.rs:    assert!(node1.swarm.transport.get_connection(node2.did()).is_none());
src/tests/default/test_connection.rs:    assert!(node2.swarm.transport.get_connection(node1.did()).is_none());
src/tests/default/mod.rs:            self.swarm.transport.get_connection_ids(),
src/tests/default/mod.rs:            self.swarm.transport.get_connections().len(),
src/tests/default/mod.rs:            assert!(self.swarm.transport.get_connection(addr).is_some());
src/tests/default/test_message_handler.rs:    let connection_1_to_2 = node1.swarm.transport.get_connection(node2.did()).unwrap();
src/tests/default/test_message_handler.rs:    let connection_2_to_3 = node2.swarm.transport.get_connection(node3.did()).unwrap();
src/tests/default/test_message_handler.rs:    let connection_1_to_3 = node1.swarm.transport.get_connection(node3.did());
src/tests/default/test_message_handler.rs:    let connection_1_to_2 = node1.swarm.transport.get_connection(node2.did()).unwrap();
src/tests/default/test_message_handler.rs:    let connection_1_to_2 = node1.swarm.transport.get_connection(node2.did()).unwrap();
src/tests/default/test_message_handler.rs:    let connection_1_to_2 = node1.swarm.transport.get_connection(node2.did()).unwrap();
src/tests/default/test_message_handler.rs:    let connection_1_to_2 = node1.swarm.transport.get_connection(node2.did()).unwrap();
src/message/handlers/connection.rs:        assert!(node1.swarm.transport.get_connection(node3.did()).is_none());
src/message/handlers/connection.rs:        assert!(node1.swarm.transport.get_connection(node3.did()).is_none());
src/message/handlers/connection.rs:            if let Some(t) = node2.swarm.transport.get_connection(node1.did()) {
src/inspect.rs:            let connections = swarm.transport.get_connections();

just hide or wrap the transport, and call functions as

swam.get_connections
swarm.get_connection_ids

[RyanKung]

I dont think match WebrtcConnectionState here is a good idea.

The keyword WebRTC and belonged details is not necessary to be known for swarm / DHT layer.

Just is_connected / is_pending / is_disconnected is fine here

[RyanKung]

What's the difference between swarm.session_sk and swarm.transport.session_sk ?

[RyanKung]

Dont expose transport, just wrap it.

[RyanKung]

transport.dht.did?
swarm.did()?
swarm.dht.did?

[RyanKung]

the SwarmTransport is actually TransportWithDHT

pub struct SwarmTransport {
    transport: Transport,
    session_sk: SessionSk,
    pub(crate) dht: Arc<PeerRing>,
    #[allow(dead_code)]
    measure: Option<MeasureImpl>,
}

[RyanKung]

Maybe just rename SwarmTransport to ConnectionManager is better.

The word Transport Connection, and the way we call them are making confuse here.

Just a metaphor, Transport is a train, Connection is a railway. getting railwayS from a train via the railway station is making no sense.