fix(apple): spawn new thread for runtime to prevent it from being taken down (#4141)

Using the current thread in apple was causing a crashloop, since
connlib's thread was taken down by the network extension after
`WrappedSession::connect` returned.

Now we force the runtime to create the thread to prevent it from being
taken down.

rust/connlib/clients/apple/src/lib.rs

@@ -209,7 +209,9 @@ impl WrappedSession {
         )
         .map_err(|e| e.to_string())?;
 
-        let runtime = tokio::runtime::Builder::new_current_thread()
+        let runtime = tokio::runtime::Builder::new_multi_thread()
+            .worker_threads(1)
+            .thread_name("connlib")
             .enable_all()
             .build()
             .map_err(|e| e.to_string())?;