Copy strategiesConfigurers when cloning WebClient.Builder

This commit fixes the missing `strategiesConfigurers` copy when the
`WebClient.Builder` is cloned.

Fixes gh-24330
See gh-24329

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClientBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -114,6 +114,7 @@ public DefaultWebClientBuilder(DefaultWebClientBuilder other) {
 		this.filters = other.filters != null ? new ArrayList<>(other.filters) : null;
 		this.connector = other.connector;
 		this.strategies = other.strategies;
+		this.strategiesConfigurers = other.strategiesConfigurers != null ? new ArrayList<>(other.strategiesConfigurers) : null;
 		this.exchangeFunction = other.exchangeFunction;
 	}