Reintroduce org.springframework.http.client.reactive.ReactorResourceFactory

This commit reintroduces a deprecated ReactorResourceFactory in
org.springframework.http.client.reactive package that extends
the one in org.springframework.http.client package to avoid an
API breaking change and to provide a smoother upgrade experience.

Closes gh-31399

spring-web/src/main/java/org/springframework/http/client/reactive/ReactorResourceFactory.java

@@ -0,0 +1,47 @@
+/*
+ * 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.http.client.reactive;
+
+import reactor.netty.resources.ConnectionProvider;
+import reactor.netty.resources.LoopResources;
+
+import org.springframework.beans.factory.DisposableBean;
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.context.Lifecycle;
+
+/**
+ * Factory to manage Reactor Netty resources, i.e. {@link LoopResources} for
+ * event loop threads, and {@link ConnectionProvider} for the connection pool,
+ * within the lifecycle of a Spring {@code ApplicationContext}.
+ *
+ * <p>This factory implements {@link InitializingBean}, {@link DisposableBean}
+ * and {@link Lifecycle} and is expected typically to be declared as a
+ * Spring-managed bean.
+ *
+ * <p>Notice that after a {@link Lifecycle} stop/restart, new instances of
+ * the configured {@link LoopResources} and {@link ConnectionProvider} are
+ * created, so any references to those should be updated.
+ *
+ * @author Rossen Stoyanchev
+ * @author Brian Clozel
+ * @author Sebastien Deleuze
+ * @since 5.1
+ * @deprecated since 6.1 due to a package change; use {@link org.springframework.http.client.ReactorResourceFactory} instead.
+ */
+@Deprecated(since = "6.1")
+public class ReactorResourceFactory extends org.springframework.http.client.ReactorResourceFactory {
+}