Previously, RouterTestingModule only assigned two of the options within ExtraOptions to the Router.
Now, it assigns the same options as RouterModule does (with the exception of enableTracing) via a
new shared function assignExtraOptionsToRouter.
Fixes#23347
PR Close#39096
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
