refactor(bootstrap): BTreeMap for overrides + simplify review

- Switch overrides from HashMap to BTreeMap — deterministic iteration by
  type, drops the manual sort when logging.
- Rename the flat_map closure's inner `ips` to `addrs` to stop shadowing
  the outer Vec<String>.
- Trim the Suite 8 TEST-NET-1 comment to keep the "why" and drop
  mechanism narration.
- Drop a redundant sleep 1 after wait — wait already blocks on exit.

src/serve.rs

@@ -59,7 +59,7 @@ pub async fn run(config_path: String) -> crate::Result<()> {
             .odoh_upstream()
             .map(|o| o.host_ip_overrides())
             .unwrap_or_default(),
-        _ => std::collections::HashMap::new(),
+        _ => std::collections::BTreeMap::new(),
     };
     let bootstrap_resolver: Arc<NumaResolver> = Arc::new(NumaResolver::new(
         &config.upstream.fallback,