build: enable bundle_dts for router package (#28833)

This PR also changes the name of `EmptyOutletComponent` to `ɵEmptyOutletComponent`. This is because `ngcc` requires the node to retain the original name while dts bundler will rename the node is it's only exported using the aliases.

Example typings files:
```ts
declare class EmptyOutletComponent {
}
export {EmptyOutletComponent as ɵEmptyOutletComponent}
```

will be emitted as
```ts
export declare class ɵEmptyOutletComponent {
}
```

PR Close #28833

packages/router/BUILD.bazel

@@ -10,6 +10,7 @@ ng_module(
             "src/**/*.ts",
         ],
     ),
+    bundle_dts = True,
     deps = [
         "//packages/common",
         "//packages/core",

packages/router/src/components/empty_outlet.ts

@@ -18,5 +18,7 @@ import {Component} from '@angular/core';
  * to this `EmptyOutletComponent`.
  */
 @Component({template: `<router-outlet></router-outlet>`})
-export class EmptyOutletComponent {
+export class ɵEmptyOutletComponent {
 }
+
+export {ɵEmptyOutletComponent as EmptyOutletComponent};

packages/router/src/private_export.ts

@@ -7,6 +7,6 @@
  */
 
 
-export {EmptyOutletComponent as ɵEmptyOutletComponent} from './components/empty_outlet';
+export {ɵEmptyOutletComponent} from './components/empty_outlet';
 export {ROUTER_PROVIDERS as ɵROUTER_PROVIDERS} from './router_module';
 export {flatten as ɵflatten} from './utils/collection';

packages/router/testing/BUILD.bazel

@@ -7,6 +7,7 @@ exports_files(["package.json"])
 ng_module(
     name = "testing",
     srcs = glob(["**/*.ts"]),
+    bundle_dts = True,
     deps = [
         "//packages/common",
         "//packages/common/testing",

packages/router/upgrade/BUILD.bazel

@@ -12,6 +12,7 @@ ng_module(
             "src/**/*.ts",
         ],
     ),
+    bundle_dts = True,
     deps = [
         "//packages/common",
         "//packages/core",