feat(@angular-devkit/build-angular): auto include @angular/platform-server/init during server builds

This changes removes the need to import `@angular/platform-server/init` in the `main.server.ts` instead we now include this as an entry-point when we are bundling as server bundle.

Author: alan-agius4

packages/angular_devkit/build_angular/src/webpack/configs/common.ts

@@ -117,6 +117,12 @@ export async function getCommonConfig(wco: WebpackConfigOptions): Promise<Config
   if (isPlatformServer) {
     // Fixes Critical dependency: the request of a dependency is an expression
     extraPlugins.push(new ContextReplacementPlugin(/@?hapi|express[\\/]/));
+
+    if (Array.isArray(entryPoints['main'])) {
+      // This import must come before any imports (direct or transitive) that rely on DOM built-ins being
+      // available, such as `@angular/elements`.
+      entryPoints['main'].unshift('@angular/platform-server/init');
+    }
   }
 
   if (polyfills?.length) {

packages/schematics/angular/universal/files/src/__main@stripTsExtension__.ts.template

@@ -1,10 +1,2 @@
-/***************************************************************************************************
- * Initialize the server environment - for example, adding DOM built-in types to the global scope.
- *
- * NOTE:
- * This import must come before any imports (direct or transitive) that rely on DOM built-ins being
- * available, such as `@angular/elements`.
- */
-import '@angular/platform-server/init';
 
 export { <%= rootModuleClassName %> } from './app/<%= stripTsExtension(rootModuleFileName) %>';