[Devtools] Look for a ReactMemoCacheSentinel on state

The polyfill doesn't have access to the fiber, and it simply uses state,
which makes it not work with the devtools.

With this PR, devtools will look for this special sentinel on very first
hook's state for this sentinel and display the Forget badge if present.

The poylfill will add this sentinel to it's state (the cache array).

Author: gsathya

packages/react-devtools-shared/src/backend/renderer.js

@@ -86,6 +86,7 @@ import {
   STRICT_MODE_SYMBOL_STRING,
   PROFILER_NUMBER,
   PROFILER_SYMBOL_STRING,
+  REACT_MEMO_CACHE_SENTINEL,
   SCOPE_NUMBER,
   SCOPE_SYMBOL_STRING,
   FORWARD_REF_NUMBER,
@@ -475,7 +476,11 @@ export function getInternalReactConstants(version: string): {
 
     let resolvedContext: any = null;
     // $FlowFixMe[incompatible-type] fiber.updateQueue is mixed
-    if (!shouldSkipForgetCheck && fiber.updateQueue?.memoCache != null) {
+    if (
+      !shouldSkipForgetCheck &&
+      (fiber.updateQueue?.memoCache != null ||
+        fiber.memoizedState?.memoizedState?.[REACT_MEMO_CACHE_SENTINEL])
+    ) {
       const displayNameWithoutForgetWrapper = getDisplayNameForFiber(
         fiber,
         true,