GH-10379: Optimize Observability API usage (#10380)

Fixes: #10379

The `ObservationRegistry.NOOP` still brings some performance overhead.

* Fix `MessageProducerSupport` & `SourcePollingChannelAdapter` to check for `isObserved()`
before using the `IntegrationObservation`

**Auto-cherry-pick to `6.5.x` & `6.4.x`**

Author: artembilan

spring-integration-core/src/main/java/org/springframework/integration/endpoint/MessageProducerSupport.java

@@ -253,12 +253,17 @@ protected void sendMessage(Message<?> message) {
 		}
 
 		try {
-			IntegrationObservation.HANDLER.observation(
-							this.observationConvention,
-							DefaultMessageReceiverObservationConvention.INSTANCE,
-							() -> new MessageReceiverContext(message, getComponentName()),
-							this.observationRegistry)
-					.observe(() -> this.messagingTemplate.send(getRequiredOutputChannel(), trackMessageIfAny(message)));
+			if (isObserved()) {
+				IntegrationObservation.HANDLER.observation(
+								this.observationConvention,
+								DefaultMessageReceiverObservationConvention.INSTANCE,
+								() -> new MessageReceiverContext(message, getComponentName()),
+								this.observationRegistry)
+						.observe(() -> sendMessageWithTracking(message));
+			}
+			else {
+				sendMessageWithTracking(message);
+			}
 		}
 		catch (RuntimeException ex) {
 			if (!sendErrorMessageIfNecessary(message, ex)) {
@@ -267,6 +272,10 @@ protected void sendMessage(Message<?> message) {
 		}
 	}
 
+	private void sendMessageWithTracking(Message<?> message) {
+		this.messagingTemplate.send(getRequiredOutputChannel(), trackMessageIfAny(message));
+	}
+
 	protected void subscribeToPublisher(Publisher<? extends Message<?>> publisher) {
 		MessageChannel channelForSubscription = getRequiredOutputChannel();