fix: replace FuturesUnordered from futures with JoinSet from tokio

FuturesUnordered is likely buggy and iroh previously switched
to JoinSet in <https://github.com/n0-computer/iroh/pull/1647>.
We also have reports with logs of background_fetch getting
stuck so apparently task cancellation after timeout does not work
as intended with FuturesUnordered.

src/accounts.rs

@@ -5,12 +5,10 @@ use std::future::Future;
 use std::path::{Path, PathBuf};
 
 use anyhow::{bail, ensure, Context as _, Result};
-use futures::stream::FuturesUnordered;
-use futures::StreamExt;
 use serde::{Deserialize, Serialize};
 use tokio::fs;
 use tokio::io::AsyncWriteExt;
-use tokio::task::JoinHandle;
+use tokio::task::{JoinHandle, JoinSet};
 use uuid::Uuid;
 
 #[cfg(not(target_os = "ios"))]
@@ -304,12 +302,6 @@ impl Accounts {
     /// This is an auxiliary function and not part of public API.
     /// Use [Accounts::background_fetch] instead.
     async fn background_fetch_no_timeout(accounts: Vec<Context>, events: Events) {
-        async fn background_fetch_and_log_error(account: Context) {
-            if let Err(error) = account.background_fetch().await {
-                warn!(account, "{error:#}");
-            }
-        }
-
         events.emit(Event {
             id: 0,
             typ: EventType::Info(format!(
@@ -317,11 +309,15 @@ impl Accounts {
                 accounts.len()
             )),
         });
-        let mut futures_unordered: FuturesUnordered<_> = accounts
-            .into_iter()
-            .map(background_fetch_and_log_error)
-            .collect();
-        while futures_unordered.next().await.is_some() {}
+        let mut set = JoinSet::new();
+        for account in accounts {
+            set.spawn(async move {
+                if let Err(error) = account.background_fetch().await {
+                    warn!(account, "{error:#}");
+                }
+            });
+        }
+        set.join_all().await;
     }
 
     /// Auxiliary function for [Accounts::background_fetch].