feat(service-worker): introduce the @angular/service-worker package (#19274)

This service worker is a conceptual derivative of the existing @angular/service-worker maintained at github.com/angular/mobile-toolkit, but has been rewritten to support use across a much wider variety of applications.

Entrypoints include:

@angular/service-worker: a library for use within Angular client apps to communicate with the service worker.
@angular/service-worker/gen: a library for generating ngsw.json files from glob-based SW config files.
@angular/service-worker/ngsw-worker.js: the bundled service worker script itself.
@angular/service-worker/ngsw-cli.js: a CLI tool for generating ngsw.json files from glob-based SW config files.

packages/service-worker/cli/rollup-cli.config.js

@@ -0,0 +1,21 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import resolve from 'rollup-plugin-node-resolve';
+
+export default {
+  entry: '../../dist/all/@angular/service-worker/cli-custom/main.js',
+  dest: '../../dist/packages-dist/service-worker/ngsw-config-tmp.js',
+  format: 'iife',
+  plugins: [resolve()],
+  external: [
+    'fs',
+    'path',
+    '@angular/service-worker/config',
+  ],
+};