Revise retry for IntegrationReactiveUtils (#3543)

Related to: https://github.com/spring-cloud/stream-applications/issues/156

The `IntegrationReactiveUtils` uses a general `Flux.retry()`
operator to always retry for all the errors.
On the other hand it has only a `.doOnError(MessagingException.class)`
which leads swallowing all the other exceptions from logs and handling.

* Replace with `retryWhen()` for the `MessagingException` predicate
failing for all other exceptions.
The end-user may add their own `retry` or error handling mechanism to
the returned `Flux` from the `IntegrationReactiveUtils`

**Cherry-pick to 5.4.x**

spring-integration-core/src/main/java/org/springframework/integration/util/IntegrationReactiveUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2020 the original author or authors.
+ * Copyright 2020-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -37,6 +37,7 @@ import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.core.publisher.Sinks;
 import reactor.core.scheduler.Schedulers;
+import reactor.util.retry.Retry;
 
 /**
  * Utilities for adapting integration components to/from reactive types.
@@ -100,7 +101,7 @@ public final class IntegrationReactiveUtils {
 										Mono.delay(ctx.getOrDefault(DELAY_WHEN_EMPTY_KEY,
 												DEFAULT_DELAY_WHEN_EMPTY)))))
 				.repeat()
-				.retry();
+				.retryWhen(Retry.indefinitely().filter(MessagingException.class::isInstance));
 	}
 
 	/**