Performance: avoid triggering map deopt in V8 (facebook#28569)

The shape of the objects changed by this PR are both created in 2
locations with 2 different shapes, which most JS engines won't like.
I've noticed this in particular in V8 while benchmarking production
code.


https://github.com/facebook/react/blob/1293047d6063f3508af15e68cca916660ded791e/packages/react-reconciler/src/ReactFiberCacheComponent.js#L66-L77


https://github.com/facebook/react/blob/1293047d6063f3508af15e68cca916660ded791e/packages/react-reconciler/src/ReactFiberHostContext.js#L47-L54


https://github.com/facebook/react/blob/1293047d6063f3508af15e68cca916660ded791e/packages/react-reconciler/src/ReactFiberHooks.js#L3530-L3531


https://github.com/facebook/react/blob/1293047d6063f3508af15e68cca916660ded791e/packages/react-reconciler/src/ReactFiberHooks.js#L3492-L3493

Author: romgrk

packages/react-reconciler/src/ReactFiberHooks.js

@@ -3489,8 +3489,8 @@ export const ContextOnlyDispatcher: Dispatcher = {
   useContext: throwInvalidHookError,
   useEffect: throwInvalidHookError,
   useImperativeHandle: throwInvalidHookError,
-  useInsertionEffect: throwInvalidHookError,
   useLayoutEffect: throwInvalidHookError,
+  useInsertionEffect: throwInvalidHookError,
   useMemo: throwInvalidHookError,
   useReducer: throwInvalidHookError,
   useRef: throwInvalidHookError,

packages/react-reconciler/src/ReactFiberHostContext.js

@@ -46,11 +46,11 @@ const hostTransitionProviderCursor: StackCursor<Fiber | null> =
 // inside useHostTransitionStatus.
 export const HostTransitionContext: ReactContext<TransitionStatus | null> = {
   $$typeof: REACT_CONTEXT_TYPE,
+  Provider: (null: any),
+  Consumer: (null: any),
   _currentValue: null,
   _currentValue2: null,
   _threadCount: 0,
-  Provider: (null: any),
-  Consumer: (null: any),
 };
 
 function requiredContext<Value>(c: Value | null): Value {