Introduce ObjectUtils.nullSafeConciseToString()

ObjectUtils.nullSafeToString(Object) exists for generating a string
representation of various objects in a "null-safe" manner, including
support for object graphs, collections, etc.

However, there are times when we would like to generate a "concise",
null-safe string representation that does not include an entire object
graph (or potentially a collection of object graphs).

This commit introduces ObjectUtils.nullSafeConciseToString(Object) to
address this need and makes use of the new feature in FieldError and
ConversionFailedException.

Closes gh-30286

spring-context/src/main/java/org/springframework/validation/FieldError.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -125,7 +125,7 @@ public class FieldError extends ObjectError {
 	@Override
 	public String toString() {
 		return "Field error in object '" + getObjectName() + "' on field '" + this.field +
-				"': rejected value [" + ObjectUtils.nullSafeToString(this.rejectedValue) + "]; " +
+				"': rejected value [" + ObjectUtils.nullSafeConciseToString(this.rejectedValue) + "]; " +
 				resolvableToString();
 	}