[TASK] Implicitly add backend routes to router using DI factories

All Routes.php information for Backend routes are now collected
via Dependency Injection.

That means Bootstrap::initializeBackendRouter() doesn't
need to be called explicitly from a middleware anymore.

The Router class will always have the routes populated
whenever it is initialized / needed.

We use DI factories to collect and add the backend routes.
The routes from the extension configuration files are still cached,
but the cache is managed by a service provider.

We adapt the ServiceProviderCompilationPass to keep track
of the return type of extended services where the extension
may not have a return type declaration (because of the
dynamic closures in PseudoServiceProvider). We do that
to properly notify symfony DI that the routes are
stored as ArrayObject.

Change-Id: Ie589825408bf9e51782800a1b8370f57d81d5178
Releases: master
Resolves: #90247
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/62531
Tested-by: Benni Mack <be...