[pulsar-proxy] fix logging for published messages (apache#6474)

### Motivation
Proxy-logging fetches incorrect producerId for `Send` command because of that logging always gets producerId as 0 and it fetches invalid topic name for the logging.

### Modification
Fixed topic logging by fetching correct producerId for `Send` command.

pulsar-proxy/src/main/java/org/apache/pulsar/proxy/server/ParserProxyHandler.java

@@ -116,7 +116,7 @@ public void channelRead(ChannelHandlerContext ctx, Object msg) {
                         logging(ctx.channel() , cmd.getType() , "", null);
                         break;
                     }
-                    topicName = TopicName.get(ParserProxyHandler.producerHashMap.get(String.valueOf(cmd.getProducer().getProducerId()) + "," + String.valueOf(ctx.channel().id())));
+                    topicName = TopicName.get(ParserProxyHandler.producerHashMap.get(String.valueOf(cmd.getSend().getProducerId()) + "," + String.valueOf(ctx.channel().id())));
                     MessageParser.parseMessage(topicName,  -1L,
                             -1L,buffer,(message) -> {
                                 messages.add(message);