iroh-net: enable cli pings or remove unused code

[divagant-martian]

We have a lot of machinery coming from tailscale to allow explicit pings from the cli:

I'm writting the explicit pieces of code because even removing one, rust is unable to identify the others as unused due to their pub declaration

1. a result type
   

   iroh/iroh-net/src/config.rs

   Lines 125 to 151 in f2f3ead

   	/// Contains response information for the "tailscale ping" subcommand,
   	/// saying how Tailscale can reach a Tailscale IP or subnet-routed IP.
   	/// See tailcfg.PingResponse for a related response that is sent back to control
   	/// for remote diagnostic pings.
   	// Based on tailscale/ipnstate
   	#[derive(Debug, Clone, PartialEq, Default)]
   	pub struct PingResult {
   	/// ping destination
   	pub ip: Option<IpAddr>,
   	/// Tailscale IP of node handling IP (different for subnet routers)
   	pub node_ip: Option<IpAddr>,
   	/// DNS name base or (possibly not unique) hostname
   	pub node_name: Option<String>,
   	/// Perceived latency in seconds.
   	pub latency_seconds: Option<f64>,
   	/// The ip:port if direct UDP was used. It is not currently set for TSMP pings.
   	pub endpoint: Option<SocketAddr>,
   	/// Non-zero DERP region ID if DERP was used. It is not currently set for TSMP pings.
   	pub derp_region_id: Option<u16>,
   	/// The three-letter region code corresponding to derp_region_id. It is not currently set for TSMP pings.
   	pub derp_region_code: Option<String>,
   	/// Whether the ping request error is due to it being a ping to the local node.
   	pub is_local_ip: Option<bool>,
   	/// Did any error occur?
   	pub err: Option<String>,
   	}

2. commented out code
   

   iroh/iroh-net/src/magicsock.rs

   Lines 515 to 548 in f2f3ead

   	// TODO
   	// /// Handles a "ping" CLI query.
   	// #[instrument(skip_all, fields(self.name = %self.name))]
   	// pub async fn ping<F>(&self, peer: config::Node, mut res: config::PingResult, cb: F)
   	// where
   	// F: Fn(config::PingResult) -> BoxFuture<'static, ()> + Send + Sync + 'static,
   	// {
   	// res.node_ip = peer.addresses.get(0).copied();
   	// res.node_name = match peer.name.as_ref().and_then(|n| n.split('.').next()) {
   	// Some(name) => {
   	// // prefer DNS name
   	// Some(name.to_string())
   	// }
   	// None => {
   	// // else hostname
   	// Some(peer.hostinfo.hostname.clone())
   	// }
   	// };
   	// let ep = self
   	// .peer_map
   	// .read()
   	// .await
   	// .endpoint_for_node_key(&peer.key)
   	// .cloned();
   	// match ep {
   	// Some(ep) => {
   	// ep.cli_ping(res, cb).await;
   	// }
   	// None => {
   	// res.err = Some("unknown peer".to_string());
   	// cb(res);
   	// }
   	// }
   	// }

3. a field to handle the pings
   

   iroh/iroh-net/src/magicsock/endpoint.rs

   Lines 71 to 72 in f2f3ead

   	/// Any outstanding "tailscale ping" commands running
   	pending_cli_pings: Vec<PendingCliPing>,

4. And its type
   

   iroh/iroh-net/src/magicsock/endpoint.rs

   Lines 80 to 85 in f2f3ead

   	#[derive(derive_more::Debug)]
   	pub struct PendingCliPing {
   	pub res: config::PingResult,
   	#[debug("cb: Box<..>")]
   	pub cb: Box<dyn Fn(config::PingResult) -> BoxFuture<'static, ()> + Send + Sync + 'static>,
   	}

5. A Enum variant for the cli ping
   

   iroh/iroh-net/src/magicsock/endpoint.rs

   Lines 1257 to 1264 in f2f3ead

   	pub enum DiscoPingPurpose {
   	/// The purpose of a ping was to see if a path was valid.
   	Discovery,
   	/// The user is running "tailscale ping" from the CLI. These types of pings can go over DERP.
   	Cli,
   	/// Ping to ensure the current route is still valid.
   	StayinAlive,
   	}

We should put this code to use or remove it