GH-9478: Fix MessagingGatewaySupport.onInit() for calling super.onInit()

Fixes: #9478
Issue link: https://github.com/spring-projects/spring-integration/issues/9478

Any `MessagingGatewaySupport` implementation does not register itself into a `SmartLifecycleRoleController`
because they don't call  `super.onInit()` of the `AbstractEndpoint`

* Fix `MessagingGatewaySupport` for calling  `super.onInit()` from its `onInit()`
* Verify `SmartLifecycleRoleController` registration in the `KafkaInboundGatewayTests`
* Remove out of use XML `group-id` attribute from Kafka channel adapter
and move it to the `channel` XSD as the place where it is really used

**Auto-cherry-pick to `6.3.x` & `6.2.x`**

spring-integration-core/src/main/java/org/springframework/integration/gateway/MessagingGatewaySupport.java

@@ -423,6 +423,7 @@ public abstract class MessagingGatewaySupport extends AbstractEndpoint
 		if (!this.replyTimeoutSet) {
 			this.messagingTemplate.setReceiveTimeout(endpointsDefaultTimeout);
 		}
+		super.onInit();
 		this.initialized = true;
 	}