Remove netty5 Unsafe class (#2338)

 Remove usage of Usafe (see netty/netty#12511).

reactor-netty-core/src/main/java/reactor/netty/transport/ServerTransport.java

@@ -437,7 +437,7 @@ void initChild(final Channel child) {
 		}
 
 		static void forceClose(Channel child, Throwable t) {
-			child.unsafe().closeForcibly();
+			child.close();
 			log.warn(format(child, "Failed to register an accepted channel: {}"), child, t);
 		}
 	}

reactor-netty-core/src/main/java/reactor/netty/transport/TransportConnector.java

@@ -323,14 +323,14 @@ static Mono<Channel> doInitAndRegister(
 								channel.close();
 							}
 							else {
-								channel.unsafe().closeForcibly();
+								channel.close();
 							}
 							monoChannelPromise.setFailure(f.cause());
 						}
 					});
 				}
 				else {
-					channel.unsafe().closeForcibly();
+					channel.close();
 					monoChannelPromise.setFailure(future.cause());
 				}
 			});

reactor-netty-core/src/test/java/reactor/netty/ReactorNettyTest.java

@@ -22,6 +22,7 @@
 import io.netty5.channel.ChannelOutboundBuffer;
 import io.netty5.channel.ChannelShutdownDirection;
 import io.netty5.channel.embedded.EmbeddedChannel;
+import io.netty5.util.concurrent.Promise;
 import org.junit.jupiter.api.Test;
 import reactor.util.annotation.Nullable;
 
@@ -123,11 +124,6 @@ static class TestChannel extends AbstractChannel {
 			this.remoteAddress = remoteAddress;
 		}
 
-		@Override
-		protected AbstractUnsafe newUnsafe() {
-			return null;
-		}
-
 		@Override
 		public SocketAddress localAddress() {
 			return localAddress0();
@@ -172,6 +168,10 @@ protected void doBeginRead() {
 		protected void doWrite(ChannelOutboundBuffer in) {
 		}
 
+		@Override
+		protected void connectTransport(SocketAddress remoteAddress, SocketAddress localAddress, Promise<Void> promise) {
+		}
+
 		@Override
 		public ChannelConfig config() {
 			return null;