Revisit meaning of response.close() in HTTP client

Prior to this issue, SPR-15920 added this new `close()` method which was
supposed to be called to clean resources after response processing.

This commit changes the meaning of that method: calling `close()` will
close the underlying HTTP connection. This has to be called if the
response body is not consumed by the application, since at that point
the underlying connection might be in an inconsistent state if shared in
a connection pool.

Issue: SPR-15993

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

@@ -43,12 +43,13 @@ public interface ClientHttpResponse extends ReactiveHttpInputMessage, Closeable
 	MultiValueMap<String, ResponseCookie> getCookies();
 
 	/**
-	 * Close this response, freeing any resources created.
-	 * <p>This non-blocking method has to be called once the response has been
-	 * processed and the resources are no longer needed; not doing so might
-	 * create resource leaks or connection issues.
-	 * <p>Depending on the client configuration and HTTP version,
-	 * this can lead to closing the connection or returning it to a connection pool.
+	 * Close this response and the underlying HTTP connection.
+	 * <p>This non-blocking method has to be called if its body isn't going
+	 * to be consumed. Not doing so might result in HTTP connection pool
+	 * inconsistencies or memory leaks.
+	 * <p>This shouldn't be called if the response body is read,
+	 * because it would prevent connections to be reused and cancel
+	 * the benefits of using a connection pooling.
 	 */
 	@Override
 	void close();