build: do not generate flat module bundles for testonly targets

This is necessary as `ng_module` rules with a `module_name` either
need a `public-api.ts` or `module.ts` file.

Author: devversion

src/cdk-experimental/testing/tests/BUILD.bazel

@@ -4,6 +4,7 @@ load("//tools:defaults.bzl", "ng_e2e_test_library", "ng_module", "ng_test_librar
 
 ng_module(
     name = "test_components",
+    testonly = True,
     srcs = glob(
         ["**/*.ts"],
         exclude = [
@@ -12,7 +13,6 @@ ng_module(
         ],
     ),
     assets = glob(["**/*.html"]),
-    module_name = "@angular/cdk-experimental/testing/tests",
     deps = [
         "//src/cdk/keycodes",
         "@npm//@angular/forms",

src/e2e-app/BUILD.bazel

@@ -13,6 +13,7 @@ exports_files([
 
 ng_module(
     name = "e2e-app",
+    testonly = True,
     srcs = glob(
         ["**/*.ts"],
         exclude = ["test-util/**"],
@@ -87,6 +88,7 @@ sass_binary(
 
 ts_devserver(
     name = "devserver",
+    testonly = True,
     # Root paths can be used simplify the loading of files from external Bazel repositories
     # (such as the Bazel managed deps repository called "npm")
     additional_root_paths = [

src/e2e-app/component-harness/component-harness-e2e-module.ts

@@ -5,7 +5,7 @@
  * 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 {TestComponentsModule} from '@angular/cdk-experimental/testing/tests';
+import {TestComponentsModule} from '../../cdk-experimental/testing/tests';
 import {CommonModule} from '@angular/common';
 import {NgModule} from '@angular/core';
 import {FormsModule} from '@angular/forms';

src/material/testing/BUILD.bazel

@@ -4,6 +4,7 @@ load("//tools:defaults.bzl", "ng_module")
 
 ng_module(
     name = "testing",
+    testonly = True,
     srcs = glob(["**/*.ts"]),
     module_name = "@angular/material/testing",
     deps = [