Move CorsHandler to server (#62007)

Currently we duplicate our specialized cors logic in all transport
plugins. This is unnecessary as it could be implemented in a single
place. This commit moves the logic to server. Additionally it fixes a
but where we are incorrectly closing http channels on early Cors
responses.

modules/transport-netty4/src/main/java/org/elasticsearch/http/netty4/Netty4HttpServerTransport.java

@@ -59,10 +59,9 @@
 import org.elasticsearch.http.HttpHandlingSettings;
 import org.elasticsearch.http.HttpReadTimeoutException;
 import org.elasticsearch.http.HttpServerChannel;
-import org.elasticsearch.http.netty4.cors.Netty4CorsHandler;
 import org.elasticsearch.threadpool.ThreadPool;
-import org.elasticsearch.transport.SharedGroupFactory;
 import org.elasticsearch.transport.NettyAllocator;
+import org.elasticsearch.transport.SharedGroupFactory;
 import org.elasticsearch.transport.netty4.Netty4Utils;
 
 import java.net.InetSocketAddress;
@@ -315,9 +314,6 @@ protected void initChannel(Channel ch) throws Exception {
                 ch.pipeline().addLast("encoder_compress", new HttpContentCompressor(handlingSettings.getCompressionLevel()));
             }
             ch.pipeline().addLast("request_creator", requestCreator);
-            if (handlingSettings.isCorsEnabled()) {
-                ch.pipeline().addLast("cors", new Netty4CorsHandler(transport.corsConfig));
-            }
             ch.pipeline().addLast("pipelining", new Netty4HttpPipeliningHandler(logger, transport.pipeliningMaxEvents));
             ch.pipeline().addLast("handler", requestHandler);
             transport.serverAcceptedChannel(nettyHttpChannel);