feature #35560 [HttpKernel] allow using public aliases to reference controllers (nicolas-grekas)

This PR was merged into the 5.1-dev branch.

Discussion
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[HttpKernel] allow using public aliases to reference controllers

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

This PR allows referencing a controller with an alias when needed. The use case I'm targetting is using `@Route` annotations on methods of the `App\Kernel` and have them work. This PR allows it.

Sidekick of symfony/recipes#735

Commits
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94bc1f7d3b [HttpKernel] allow using public aliases to reference controllers

Author: fabpot

Kernel/MicroKernelTrait.php

@@ -141,7 +141,7 @@ public function registerContainerConfiguration(LoaderInterface $loader)
                 AbstractConfigurator::$valuePreProcessor = $valuePreProcessor;
             }
 
-            $container->setAlias(static::class, 'kernel');
+            $container->setAlias(static::class, 'kernel')->setPublic(true);
         });
     }