Make CodecException handling consistent

This commit makes CodecException handling consistent between functional
and annotation-based APIs. It now returns by default 4xx status code
for decoding error and 5xx for encoding error + print the error reason
in logs without the full stack trace in both variants.

Issue: SPR-15355

spring-webflux/src/test/java/org/springframework/web/reactive/DispatcherHandlerErrorTests.java

@@ -102,7 +102,7 @@ public class DispatcherHandlerErrorTests {
 		Mono<Void> publisher = this.dispatcherHandler.handle(exchange);
 
 		StepVerifier.create(publisher)
-				.consumeErrorWith(error -> assertSame(EXCEPTION, error))
+				.consumeErrorWith(error -> assertSame(EXCEPTION, error.getCause()))
 				.verify();
 	}