[lib] Stop processOutboundMessages loop when it becomes outdated

Summary:
This addresses [ENG-9454](https://linear.app/comm/issue/ENG-9454/cannot-read-properties-of-undefined-when-leaving-thread) and [ENG-9448](https://linear.app/comm/issue/ENG-9448/robotext-doesnt-display-for-first-farcaster-mutual).

When we update this callback, we should make sure we stop running old versions of the callback. Otherwise, there's a risk that we'll process new data with callbacks that are bound to old versions of the Redux state.

Test Plan:
I had a repro of ENG-9448 where I simply logged out and back in with my `t125` test user. After this diff:

1. I no longer see `Cannot read properties of undefined` errors
2. The robotext messages are delivered for all of my Farcaster friends

Reviewers: varun, will, tomek, kamil

Reviewed By: varun

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D13563

lib/tunnelbroker/peer-to-peer-context.js

@@ -290,8 +290,10 @@ function PeerToPeerProvider(props: Props): React.Node {
     [allPeerDevices],
   );
 
-  const processOutboundMessages = React.useCallback(
-    (
+  const processOutboundMessagesLatestVersionRef = React.useRef(-1);
+  const processOutboundMessages = React.useMemo(() => {
+    const currentVersion = ++processOutboundMessagesLatestVersionRef.current;
+    return (
       outboundMessageIDs: ?$ReadOnlyArray<string>,
       dmOpID: ?string,
       notificationsCreationData: ?NotificationsCreationData,
@@ -306,6 +308,11 @@ function PeerToPeerProvider(props: Props): React.Node {
         promiseRunning.current = true;
         void (async () => {
           do {
+            if (
+              currentVersion !== processOutboundMessagesLatestVersionRef.current
+            ) {
+              break;
+            }
             const queueFront = processingQueue.current.shift();
             try {
               const [result] = await Promise.all([
@@ -343,15 +350,14 @@ function PeerToPeerProvider(props: Props): React.Node {
           promiseRunning.current = false;
         })();
       }
-    },
-    [
-      allPeerDevicesSet,
-      sendMessageToDevice,
-      identityContext,
-      peerOlmSessionsCreator,
-      sendPushNotifs,
-    ],
-  );
+    };
+  }, [
+    allPeerDevicesSet,
+    sendMessageToDevice,
+    identityContext,
+    peerOlmSessionsCreator,
+    sendPushNotifs,
+  ]);
 
   const broadcastEphemeralMessage = React.useCallback(
     async (