fix(messenger): namespace bus.name attribute as symfony.messenger.bus.name

bus.name is not a standard OTel semantic convention. Rename to
symfony.messenger.bus.name to follow the existing codebase pattern
(symfony.console.*, symfony.kernel.*).

Only changes the worker subscriber attribute; the pre-existing
bus.name in TraceableMessengerStack is left unchanged (out of scope).

Author: gaelreyrol

src/Instrumentation/Symfony/Messenger/WorkerMessageEventSubscriber.php

@@ -72,7 +72,7 @@ public function startSpan(WorkerMessageReceivedEvent $event): void
         $busNameStamp = $event->getEnvelope()->last(BusNameStamp::class);
 
         if (null !== $busNameStamp) {
-            $span->setAttribute('bus.name', $busNameStamp->getBusName());
+            $span->setAttribute('symfony.messenger.bus.name', $busNameStamp->getBusName());
         }
 
         $this->logger->debug(sprintf('Starting span "%s"', $span->getContext()->getSpanId()));

tests/Functional/Instrumentation/Messenger/MessengerWorkerTracingTest.php

@@ -49,7 +49,7 @@ public function testWorkerMessageHandled(): void
         self::assertSpanAttributesSubSet($span, [
             'messaging.operation.type' => 'process',
             'messaging.destination.name' => 'main',
-            'bus.name' => 'messenger.bus.default',
+            'symfony.messenger.bus.name' => 'messenger.bus.default',
         ]);
         self::assertSpanEventsCount($span, 0);
     }
@@ -89,7 +89,7 @@ public function testWorkerMessageFailed(): void
         self::assertSpanAttributesSubSet($span, [
             'messaging.operation.type' => 'process',
             'messaging.destination.name' => 'main',
-            'bus.name' => 'messenger.bus.default',
+            'symfony.messenger.bus.name' => 'messenger.bus.default',
         ]);
         self::assertSpanEventsCount($span, 1);