sync: add owned future for CancellationToken (#5153)

tokio-util/src/sync/tests/loom_cancellation_token.rs

@@ -24,6 +24,27 @@ fn cancel_token() {
     });
 }
 
+#[test]
+fn cancel_token_owned() {
+    loom::model(|| {
+        let token = CancellationToken::new();
+        let token1 = token.clone();
+
+        let th1 = thread::spawn(move || {
+            block_on(async {
+                token1.cancelled_owned().await;
+            });
+        });
+
+        let th2 = thread::spawn(move || {
+            token.cancel();
+        });
+
+        assert_ok!(th1.join());
+        assert_ok!(th2.join());
+    });
+}
+
 #[test]
 fn cancel_with_child() {
     loom::model(|| {