Add ReactDOMClient to ServerIntegrationBasic (#28133)

## Overview

Branched off #28130

In `hydrateRoot`, we now error if you pass `undefined`:

```
Warning: Must provide initial children as second argument to hydrateRoot. 
```

So we expect 1 error for this now.

packages/react-dom/src/__tests__/ReactDOMServerIntegrationBasic-test.js

@@ -15,21 +15,21 @@ const ReactDOMServerIntegrationUtils = require('./utils/ReactDOMServerIntegratio
 const TEXT_NODE_TYPE = 3;
 
 let React;
-let ReactDOM;
+let ReactDOMClient;
 let ReactDOMServer;
 let ReactTestUtils;
 
 function initModules() {
   // Reset warning cache.
   jest.resetModules();
   React = require('react');
-  ReactDOM = require('react-dom');
+  ReactDOMClient = require('react-dom/client');
   ReactDOMServer = require('react-dom/server');
   ReactTestUtils = require('react-dom/test-utils');
 
   // Make them available to the helpers.
   return {
-    ReactDOM,
+    ReactDOMClient,
     ReactDOMServer,
     ReactTestUtils,
   };
@@ -149,8 +149,10 @@ describe('ReactDOMServerIntegration', () => {
       expect(await render([])).toBe(null);
       expect(await render(false)).toBe(null);
       expect(await render(true)).toBe(null);
-      expect(await render(undefined)).toBe(null);
       expect(await render([[[false]], undefined])).toBe(null);
+
+      // hydrateRoot errors for undefined children.
+      expect(await render(undefined, 1)).toBe(null);
     });
   });
 });