Refactor React Server entrypoint to not depend on the client one (#27940)

This refactors the Server Components entrypoint for the `react` package
(ReactServer.js) so that it doesn't depend on the client entrypoint
(React.js). I also renamed React.js to ReactClient.js to make the
separation clearer.

This structure will make it easier to add client-only and server-only
features.

Author: acdlite

packages/react/index.classic.fb.js

@@ -58,5 +58,5 @@ export {
   useSyncExternalStore,
   useTransition,
   version,
-} from './src/React';
+} from './src/ReactClient';
 export {jsx, jsxs, jsxDEV} from './src/jsx/ReactJSX';

packages/react/index.experimental.js

@@ -57,9 +57,9 @@ export {
   useSyncExternalStore,
   useTransition,
   version,
-} from './src/React';
+} from './src/ReactClient';
 
-import {useOptimistic} from './src/React';
+import {useOptimistic} from './src/ReactClient';
 
 export function experimental_useOptimistic<S, A>(
   passthrough: S,

packages/react/index.js

@@ -80,4 +80,4 @@ export {
   useState,
   useTransition,
   version,
-} from './src/React';
+} from './src/ReactClient';

packages/react/index.modern.fb.js

@@ -56,5 +56,5 @@ export {
   useSyncExternalStore,
   useTransition,
   version,
-} from './src/React';
+} from './src/ReactClient';
 export {jsx, jsxs, jsxDEV} from './src/jsx/ReactJSX';

packages/react/index.stable.js

@@ -47,4 +47,4 @@ export {
   useSyncExternalStore,
   useTransition,
   version,
-} from './src/React';
+} from './src/ReactClient';

packages/react/src/React.js renamed to packages/react/src/ReactClient.js

@@ -26,9 +26,9 @@ import {Component, PureComponent} from './ReactBaseClasses';
 import {createRef} from './ReactCreateRef';
 import {forEach, map, count, toArray, only} from './ReactChildren';
 import {
-  createElement as createElementProd,
-  createFactory as createFactoryProd,
-  cloneElement as cloneElementProd,
+  createElement,
+  createFactory,
+  cloneElement,
   isValidElement,
 } from './ReactElement';
 import {createContext} from './ReactContext';
@@ -61,27 +61,12 @@ import {
   useMemoCache,
   useOptimistic,
 } from './ReactHooks';
-import {
-  createElementWithValidation,
-  createFactoryWithValidation,
-  cloneElementWithValidation,
-} from './ReactElementValidator';
+
 import {createServerContext} from './ReactServerContext';
 import ReactSharedInternals from './ReactSharedInternalsClient';
 import {startTransition} from './ReactStartTransition';
 import {act} from './ReactAct';
 
-// TODO: Move this branching into the other module instead and just re-export.
-const createElement: any = __DEV__
-  ? createElementWithValidation
-  : createElementProd;
-const cloneElement: any = __DEV__
-  ? cloneElementWithValidation
-  : cloneElementProd;
-const createFactory: any = __DEV__
-  ? createFactoryWithValidation
-  : createFactoryProd;
-
 const Children = {
   map,
   forEach,