By default set client idle timeout (#2371)

Having no idle timeout by default is not the right choice. Most modern environments (e.g. every cloud, every proxy) forget about idle connections fairly quickly. For example, I have worked with proxies that forgot about connections after an idle time of as low as 90 seconds.

In this change we set the default idle time to 50 seconds.

zio-http/src/main/scala/zio/http/ZClient.scala

@@ -608,7 +608,7 @@ object ZClient {
       localAddress = None,
       addUserAgentHeader = true,
       webSocketConfig = WebSocketConfig.default,
-      idleTimeout = None,
+      idleTimeout = Some(50.seconds),
       connectionTimeout = None,
     )
   }