[Messenger] Add existing tags to unused whitelist

Author: Robin Chalas

src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/UnusedTagsPass.php

@@ -39,6 +39,10 @@ class UnusedTagsPass implements CompilerPassInterface
         'kernel.event_listener',
         'kernel.event_subscriber',
         'kernel.fragment_renderer',
+        'messenger.bus',
+        'messenger.sender',
+        'messenger.receiver',
+        'messenger.message_handler',
         'monolog.logger',
         'routing.expression_language_provider',
         'routing.loader',