[11.x] Allow RouteServiceProvider to be loaded more than once

[crynobone]

With the new ApplicationBuilder::withRouting(), Laravel now registers RouteServiceProvider and this causes breaking changes to any applications or existing packages already extending RouteServiceProvider. While we can argue that ApplicationBuilder should only be used for new Laravel application it still cause breaking changes for multiple packages including: https://github.com/search?q=Illuminate%5CFoundation%5CSupport%5CProviders%5CRouteServiceProvider+language%3APHP+path%3A%2F%5Esrc%5C%2F%2F&type=code

[ahmedsayedabdelsalam]

forcing it will make the framework route service provider run last so if i need to override loadCachedRoutes method as an example it will not work mcamara/laravel-localization#899