Revise contribution

This commit reverts changes to AbstractCacheManager since iterating
over the caches in a for-loop and a stream is duplicated effort.

This commit reverts changes to DefaultRenderingResponseBuilder,
RouterFunctions, and OriginHandshakeInterceptor since order matters for
those use cases: they were originally based on the semantics of
LinkedHashSet or LinkedHashMap; whereas, Set.copyOf() and Map.copyOf()
do not provide any guarantees regarding ordering.

This commit also applies analogous changes to "sibling" implementations
across Servlet mocks as well as Web MVC and WebFlux.

See gh-29321

spring-test/src/main/java/org/springframework/mock/web/HeaderValueHolder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 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.