fix(iroh-net): Do not return a port for reqwest DNS resolver (#2906)

## Description

A non-zero port is interpreted as overriding the port specified or
implied by the URL.  Despite the docs not telling you this.  That's
not really what we want here.

## Breaking Changes

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

## Notes & open questions


seanmonstar/reqwest#2413 (comment)

## Change checklist

- [x] Self-review.
- [x] Documentation updates following the [style
guide](https://rust-lang.github.io/rfcs/1574-more-api-documentation-conventions.html#appendix-a-full-conventions-text),
if relevant.
- [x] Tests if relevant.
- [x] All breaking changes documented.

iroh-net/src/netcheck/reportgen.rs

@@ -891,15 +891,14 @@ async fn check_captive_portal(
     if let Some(Host::Domain(domain)) = url.host() {
         // Use our own resolver rather than getaddrinfo
         //
-        // For some reason reqwest wants SocketAddr rather than IpAddr but then proceeds to
-        // ignore the port, extracting it from the URL instead.  We supply a dummy port.
+        // Be careful, a non-zero port will override the port in the URI.
         //
         // Ideally we would try to resolve **both** IPv4 and IPv6 rather than purely race
         // them.  But our resolver doesn't support that yet.
         let addrs: Vec<_> = dns_resolver
             .lookup_ipv4_ipv6_staggered(domain, DNS_TIMEOUT, DNS_STAGGERING_MS)
             .await?
-            .map(|ipaddr| SocketAddr::new(ipaddr, 80))
+            .map(|ipaddr| SocketAddr::new(ipaddr, 0))
             .collect();
         builder = builder.resolve_to_addrs(domain, &addrs);
     }
@@ -1062,16 +1061,15 @@ async fn measure_https_latency(
     if let Some(Host::Domain(domain)) = url.host() {
         // Use our own resolver rather than getaddrinfo
         //
-        // For some reason reqwest wants SocketAddr rather than IpAddr but then proceeds to
-        // ignore the port, extracting it from the URL instead.  We supply a dummy port.
+        // Be careful, a non-zero port will override the port in the URI.
         //
         // The relay Client uses `.lookup_ipv4_ipv6` to connect, so use the same function
         // but staggered for reliability.  Ideally this tries to resolve **both** IPv4 and
         // IPv6 though.  But our resolver does not have a function for that yet.
         let addrs: Vec<_> = dns_resolver
             .lookup_ipv4_ipv6_staggered(domain, DNS_TIMEOUT, DNS_STAGGERING_MS)
             .await?
-            .map(|ipaddr| SocketAddr::new(ipaddr, 80))
+            .map(|ipaddr| SocketAddr::new(ipaddr, 0))
             .collect();
         builder = builder.resolve_to_addrs(domain, &addrs);
     }