Use the inner unfiltered Promise's stack as the best stack describing I/O

Author: sebmarkbage

packages/react-server/src/ReactFlightServer.js

@@ -1935,6 +1935,10 @@ function visitAsyncNode(
               ioNode.end = node.end;
             }
             match = ioNode;
+          } else if (ioNode.tag === PROMISE_NODE) {
+            // If the ioNode was a Promise, then that means we found one in user space since otherwise
+            // we would've returned an IO node. We assume this has the best stack.
+            match = ioNode;
           } else {
             match = node;
           }