Initialize Map with correct size in RequestPredicates

Prior to this commit, the `RequestPredicates` would add new attributes
to the existing request attributes by creating a new `LinkedHashMap`
with the total number of elements as its new initial capacity.

This would not achieve optimal performance as initial resize or rehash
operations could be expected. Consistently using
`CollectionUtils#newLinkedHashMap` avoids this problem.

Closes gh-32201

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/RequestPredicates.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -49,6 +49,7 @@
 import org.springframework.lang.NonNull;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
 import org.springframework.util.MimeTypeUtils;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.bind.WebDataBinder;
@@ -325,7 +326,7 @@ private static <K, V> Map<K, V> mergeMaps(Map<K, V> left, Map<K, V> right) {
 				return left;
 			}
 			else {
-				Map<K, V> result = new LinkedHashMap<>(left.size() + right.size());
+				Map<K, V> result = CollectionUtils.newLinkedHashMap(left.size() + right.size());
 				result.putAll(left);
 				result.putAll(right);
 				return result;

spring-webmvc/src/main/java/org/springframework/web/servlet/function/RequestPredicates.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -51,6 +51,7 @@
 import org.springframework.lang.NonNull;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
 import org.springframework.util.MimeTypeUtils;
 import org.springframework.util.MultiValueMap;
 import org.springframework.validation.BindException;
@@ -324,7 +325,7 @@ private static <K, V> Map<K, V> mergeMaps(Map<K, V> left, Map<K, V> right) {
 				return left;
 			}
 			else {
-				Map<K, V> result = new LinkedHashMap<>(left.size() + right.size());
+				Map<K, V> result = CollectionUtils.newLinkedHashMap(left.size() + right.size());
 				result.putAll(left);
 				result.putAll(right);
 				return result;