Preemptively close the channel when receiving SslCloseCompletionEvent

[yzfeng2020]

Sometimes a server can throw the following exception io.netty.handler.ssl.SslClosedEngineException: SSLEngine closed already, - a remote peer can send a CLOSE_NOTIFY with its last SSL packet, which immediately closes the SSL engine. Armeria won't know about it until an attempt is made to send a message over that connection. Since the SSL engine is closed by that point, a SslClosedEngineException will be thrown. The right way to handle this is to preemptively close the engine.

[jrhee17]

discussion ref: https://discord.com/channels/1087271586832318494/1087272728177942629/1223443540982370407