Event Loop shutdown stuck due to uncompleted connect (#Fixes 192)

Motivation:

uncompleted CONNECT_SCHEDULE prevent force closing and issuing IORING_OP_CLOSE, causing a graceful shutdown
to complete its quiet period and ignore any later CONNECT completion (at the mercy of OS configuration for connect timeout)
due to already shutdown executor.
This will cause the executor to not be able to complete its cleanup because of unclosed channels and making it to hang awaiting
an already happened CQE.

Modification:

Allow force close to initiate a close despite the uncompleted CONNECT_SCHEDULE, allowing it to issue a IORING_OP_CLOSE.
When the FD close would complete, a later CQE of CONNECT_SCHEDULE on the closed FD will be ignored because its channel is already deregistered.

Result:

Prompt channel close on short timeout (regardless peer presence)

transport-classes-io_uring/src/main/java/io/netty/incubator/channel/uring/AbstractIOUringChannel.java

@@ -336,7 +336,8 @@ abstract class AbstractUringUnsafe extends AbstractUnsafe {
 
         @Override
         public void close(ChannelPromise promise) {
-            if ((ioState & (WRITE_SCHEDULED | READ_SCHEDULED | CONNECT_SCHEDULED)) == 0) {
+            if ((ioState & (WRITE_SCHEDULED | READ_SCHEDULED)) == 0) {
+                // force close can ignore any CONNECT_SCHEDULED
                 forceClose(promise);
             } else {
                 if (delayedClose == null || delayedClose.isVoid()) {

transport-native-io_uring/src/test/java/io/netty/incubator/channel/uring/IOUringClientSocketConnectionShortTimeoutTest.java

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2021 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.incubator.channel.uring;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+import io.netty.bootstrap.Bootstrap;
+import io.netty.channel.ChannelFuture;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelOption;
+import io.netty.channel.ConnectTimeoutException;
+import io.netty.channel.DefaultEventLoopGroup;
+import io.netty.channel.SimpleChannelInboundHandler;
+import io.netty.channel.socket.nio.NioSocketChannel;
+import io.netty.testsuite.transport.TestsuitePermutation;
+import io.netty.testsuite.transport.socket.AbstractClientSocketTest;
+import org.hamcrest.MatcherAssert;
+import org.hamcrest.core.IsInstanceOf;
+import org.junit.Assert;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInfo;
+import org.junit.jupiter.api.Timeout;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.core.IsInstanceOf.instanceOf;
+import static org.junit.jupiter.api.Assumptions.assumeTrue;
+
+public class IOUringClientSocketConnectionShortTimeoutTest extends AbstractClientSocketTest {
+
+   @BeforeAll
+   public static void loadJNI() {
+      assumeTrue(IOUring.isAvailable());
+   }
+
+   @Test
+   @Timeout(value = 30000, unit = TimeUnit.MILLISECONDS)
+   public void testConnectTimeoutAndClose(TestInfo testInfo) throws Throwable {
+      run(testInfo, (bootstrap) -> {
+         testFailedConnectWithSuperShortTimeout(bootstrap);
+         try {
+            bootstrap.config().group().shutdownGracefully().sync();
+         } catch (Throwable t) {
+            t.printStackTrace();
+         }
+      });
+   }
+
+   public void testFailedConnectWithSuperShortTimeout(Bootstrap cb) throws Throwable {
+      cb.handler(new SimpleChannelInboundHandler<Object>() {
+         @Override
+         public void channelRead0(ChannelHandlerContext ctx, Object msgs) {
+            // Nothing will be sent.
+         }
+      });
+      cb.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 1);
+      ChannelFuture future = cb.connect("198.51.100.254", 65535);
+      try {
+         assertThat(future.await(Integer.MAX_VALUE), is(true));
+      } finally {
+         Assert.assertNotNull(future.cause());
+         MatcherAssert.assertThat(future.cause(), instanceOf(ConnectTimeoutException.class));
+      }
+   }
+
+   @Override
+   protected List<TestsuitePermutation.BootstrapFactory<Bootstrap>> newFactories() {
+      return Arrays.asList(() -> new Bootstrap().group(new IOUringEventLoopGroup(1)).channel(IOUringSocketChannel.class));
+   }
+}