perf: remove react dom legacy from app router (#56082)

This PR includes changes to Next.js bundling in order to aliases references to the `react-dom/server` legacy build to a no-op in order to save KBs. We don't use any of the legacy methods so it's best to just shave it off. This should improve cold boots for both edge and regular servers.

Before:
<img width="622" alt="CleanShot 2023-09-27 at 13 30 47@2x" src="https://github.com/vercel/next.js/assets/11064311/fa383000-c71e-420e-9daa-b8d93ff242e7">

After:
<img width="622" alt="CleanShot 2023-09-27 at 13 31 32@2x" src="https://github.com/vercel/next.js/assets/11064311/702f083a-705f-4b12-9133-9bb7eb02109e">

A win of 70KBs.

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packages/next/src/build/noop-react-dom-server-legacy.ts

@@ -0,0 +1,10 @@
+const ERROR_MESSAGE =
+  'Internal Error: do not use legacy react-dom/server APIs. If you encountered this error, please open an issue on the Next.js repo.'
+
+export function renderToString() {
+  throw new Error(ERROR_MESSAGE)
+}
+
+export function renderToStaticMarkup() {
+  throw new Error(ERROR_MESSAGE)
+}

packages/next/src/build/webpack-config.ts

@@ -222,7 +222,6 @@ function createRSCAliases(
         'react/jsx-dev-runtime$': `next/dist/server/future/route-modules/app-page/vendored/shared/react-jsx-dev-runtime`,
         react$: `next/dist/server/future/route-modules/app-page/vendored/${opts.layer}/react`,
         'react-dom$': `next/dist/server/future/route-modules/app-page/vendored/${opts.layer}/react-dom`,
-        'react-dom/server.edge$': `next/dist/server/future/route-modules/app-page/vendored/${opts.layer}/react-dom-server-edge`,
         'react-server-dom-webpack/client.edge$': `next/dist/server/future/route-modules/app-page/vendored/${opts.layer}/react-server-dom-webpack-client-edge`,
       })
     } else if (opts.layer === WEBPACK_LAYERS.reactServerComponents) {

packages/next/webpack.config.js

@@ -21,7 +21,7 @@ const pagesExternals = [
 ]
 
 function makeAppAliases(reactChannel = '') {
-  const alias = {
+  return {
     react$: `next/dist/compiled/react${reactChannel}`,
     'react/shared-subset$': `next/dist/compiled/react${reactChannel}/react.shared-subset`,
     'react-dom/server-rendering-stub$': `next/dist/compiled/react-dom${reactChannel}/server-rendering-stub`,
@@ -36,9 +36,10 @@ function makeAppAliases(reactChannel = '') {
     'react-server-dom-webpack/client.edge$': `next/dist/compiled/react-server-dom-webpack${reactChannel}/client.edge`,
     'react-server-dom-webpack/server.edge$': `next/dist/compiled/react-server-dom-webpack${reactChannel}/server.edge`,
     'react-server-dom-webpack/server.node$': `next/dist/compiled/react-server-dom-webpack${reactChannel}/server.node`,
+    // optimisations to ignore the legacy build of react-dom/server
+    './cjs/react-dom-server-legacy.browser.production.min.js': `next/dist/build/noop-react-dom-server-legacy`,
+    './cjs/react-dom-server-legacy.browser.development.js': `next/dist/build/noop-react-dom-server-legacy`,
   }
-
-  return alias
 }
 
 const appAliases = makeAppAliases()