Assign resolved outlined props to element object (and not only tuple)

When an element is used multiple times as shown in facebook#30526, its props
might be deduped. When resolving the reference to the deduped props, we
were only updating the React element tuple, which at this point has
already been parsed into a React element object, using `null` as
placeholder props. Therefore, updating the element tuple doesn't help
much, and we need to make sure that the element object's props are
updated as well.

This is a similar fix as facebook#28669, see the code lines above, and thus
feels similarly hacky. Maybe there's a better way to fix this? @eps1lon
was mentioning offline that solving [this
TODO](https://github.com/facebook/react/blob/33e54fa252b9dbe7553ef42a2287c3dbbd4f035d/packages/react-client/src/ReactFlightClient.js#L1327)
would probably fix it properly, since we wouldn't need to deal with
stale tuples then. But that's a way heavier lift.

Author: unstubbable

packages/react-client/src/ReactFlightClient.js

@@ -902,6 +902,20 @@ function waitForReference<T>(
       handler.value = parentObject[key];
     }
 
+    // If the parent object is an unresolved React element tuple and its
+    // outlined props have now been resolved, we also need to update the props
+    // of the resolved element (i.e. handler.value).
+    if (
+      parentObject[0] === REACT_ELEMENT_TYPE &&
+      key === '3' &&
+      typeof handler.value === 'object' &&
+      handler.value !== null &&
+      handler.value.$$typeof === REACT_ELEMENT_TYPE &&
+      handler.value.props === null
+    ) {
+      handler.value.props = parentObject[key];
+    }
+
     handler.deps--;
 
     if (handler.deps === 0) {