Use single entry point for SSR via browser field (#10362)

* Use single entry point for SSR via browser field

* Add server.browser entry point and smoke tests

* Tweak bundle naming

* Fix import

* Re-record

* Fix the robot nits

* Add resetModules for some extra isolation

src/node_modules/react-dom/server.browser.js

@@ -10,5 +10,5 @@ var ReactDOMFeatureFlags = require('ReactDOMFeatureFlags');
 var useFiber = ReactDOMFeatureFlags.useFiber;
 
 module.exports = useFiber
-  ? require('ReactDOMNodeStreamEntry')
-  : null;
+  ? require('ReactDOMServerBrowserEntry')
+  : require('ReactDOMServerStackEntry');

src/node_modules/react-dom/server.js

@@ -10,5 +10,5 @@ var ReactDOMFeatureFlags = require('ReactDOMFeatureFlags');
 var useFiber = ReactDOMFeatureFlags.useFiber;
 
 module.exports = useFiber
-  ? require('ReactDOMServerEntry')
+  ? require('ReactDOMServerNodeEntry')
   : require('ReactDOMServerStackEntry');