build: create dev-infra-private npm package (#35862)

Creates the scaffolding for an @angular/dev-infra-private package
which will not be published to npm but will be pushed to
https://github.com/angular/dev-infra-private-builds repo for each
commit to master.

The contents of this npm package will then be depended on via
package.json dependency for angular/angular angular/angular-cli and
angular/components.

PR Close #35862

dev-infra/cli.ts

@@ -0,0 +1,14 @@
+/**
+ * @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
+ */
+const args = process.argv.slice(2);
+
+// TODO(josephperrott): Set up proper cli flag/command handling
+switch(args[0]) {
+  default:
+    console.info('No commands were matched');
+}