perf(@angular-devkit/build-angular): only rebundle server polyfills on explicit changes

The newly introduced incremental bundler result caching is now used for server polyfills. This allows the bundling steps to be skipped in watch mode when no related files have been modified.

(cherry picked from commit 51351bf)

Author: alan-agius4

packages/angular_devkit/build_angular/src/tools/esbuild/application-code-bundle.ts

@@ -250,7 +250,7 @@ export function createServerPolyfillBundleOptions(
   options: NormalizedApplicationBuildOptions,
   target: string[],
   sourceFileCache?: SourceFileCache,
-): BuildOptions | undefined {
+): BundlerOptionsFactory | undefined {
   const polyfills: string[] = [];
   const zoneFlagsNamespace = 'angular:zone-flags/placeholder';
   const polyfillsFromConfig = new Set(options.polyfills);
@@ -329,7 +329,7 @@ export function createServerPolyfillBundleOptions(
 
   buildOptions.plugins.push(createRxjsEsmResolutionPlugin());
 
-  return buildOptions;
+  return () => buildOptions;
 }
 
 function getEsBuildCommonOptions(options: NormalizedApplicationBuildOptions): BuildOptions {