feat(cli): add metrics server to iroh doctor (#2292)

## Description

Folks try to look at metrics while doctor alone is running (note this
clashes by default with the iroh node if both are running locally on
port :9090). Also kind of inconvenient given if you want to look at a
running iroh node when doctor is running.

Suggestions welcome, maybe default off metrics on `doctor`?

Also most metrics are not really used in the `doctor` path, but we can
fix that as we figure out what's cool to measure.

## Breaking Changes

<!-- Optional, if there are any breaking changes document them,
including how to migrate older code. -->

## Notes & open questions

<!-- Any notes, remarks or open questions you have to make about the PR.
-->

## Change checklist

- [x] Self-review.
- [ ] Documentation updates if relevant.
- [ ] Tests if relevant.
- [ ] All breaking changes documented.

iroh-cli/src/commands.rs

@@ -37,7 +37,7 @@ pub(crate) struct Cli {
     #[clap(long, global = true)]
     start: bool,
 
-    /// Port to serve metrics on. -1 to disable.
+    /// Port to serve metrics on. Disabled by default.
     #[clap(long)]
     pub(crate) metrics_port: Option<MetricsPort>,
 }
@@ -184,7 +184,13 @@ impl Cli {
                 .await
             }
             Commands::Doctor { command } => {
-                let config = NodeConfig::load(self.config.as_deref()).await?;
+                let mut config = NodeConfig::load(self.config.as_deref()).await?;
+                if let Some(metrics_port) = self.metrics_port {
+                    config.metrics_addr = match metrics_port {
+                        MetricsPort::Disabled => None,
+                        MetricsPort::Port(port) => Some(([127, 0, 0, 1], port).into()),
+                    };
+                }
                 self::doctor::run(command, &config).await
             }
         }

iroh-cli/src/commands/doctor.rs

@@ -1068,7 +1068,8 @@ fn inspect_ticket(ticket: &str, zbase32: bool) -> anyhow::Result<()> {
 pub async fn run(command: Commands, config: &NodeConfig) -> anyhow::Result<()> {
     let data_dir = iroh_data_root()?;
     let _guard = crate::logging::init_terminal_and_file_logging(&config.file_logs, &data_dir)?;
-    match command {
+    let metrics_fut = super::start::start_metrics_server(config.metrics_addr);
+    let cmd_res = match command {
         Commands::Report {
             stun_host,
             stun_port,
@@ -1200,7 +1201,11 @@ pub async fn run(command: Commands, config: &NodeConfig) -> anyhow::Result<()> {
 
             Ok(())
         }
+    };
+    if let Some(metrics_fut) = metrics_fut {
+        metrics_fut.abort();
     }
+    cmd_res
 }
 
 async fn run_plotter<B: Backend>(