Fix preemptive connection dropping during shutdown process (#8546)

LICENSE.md

@@ -53,4 +53,5 @@ Nick Hensel <nickhensel25@icloud.com>
 vytskalt <vytskalt@protonmail.com>
 TheFruxz <cedricspitzer@outlook.de>
 Kieran Wallbanks <kieran.wallbanks@gmail.com>
+Denery <dorofeevij@gmail.com>
 ```

patches/server/0949-Fix-player-kick-on-shutdown.patch

@@ -0,0 +1,23 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Denery <dorofeevij@gmail.com>
+Date: Sun, 6 Nov 2022 02:02:46 +0300
+Subject: [PATCH] Fix player kick on shutdown
+
+Fix preemptive player kick on a server shutdown.
+If you update minecraft version / upstream and something is changed in this method make sure that a server doesn't disconnect a player preemptively,
+also check if all packets are ignored during the shutdown process.
+See net.minecraft.network.Connection#channelRead0(ChannelHandlerContext, Packet) and net.minecraft.util.thread.BlockableEventLoop#executeIfPossible(Runnable)
+
+diff --git a/src/main/java/net/minecraft/network/protocol/PacketUtils.java b/src/main/java/net/minecraft/network/protocol/PacketUtils.java
+index 8bc0cb9ad5bb4e76d962ff54305e2c08e279a17b..edefab4e22ee7217e17eb036165ce58788d4c782 100644
+--- a/src/main/java/net/minecraft/network/protocol/PacketUtils.java
++++ b/src/main/java/net/minecraft/network/protocol/PacketUtils.java
+@@ -41,7 +41,7 @@ public class PacketUtils {
+ 
+     public static <T extends PacketListener> void ensureRunningOnSameThread(Packet<T> packet, T listener, BlockableEventLoop<?> engine) throws RunningOnDifferentThreadException {
+         if (!engine.isSameThread()) {
+-            engine.executeIfPossible(() -> {
++            engine.execute(() -> { // Paper - Fix preemptive player kick on a server shutdown. 
+                 packetProcessing.push(listener); // Paper - detailed watchdog information
+                 try { // Paper - detailed watchdog information
+                 if (MinecraftServer.getServer().hasStopped() || (listener instanceof ServerGamePacketListenerImpl && ((ServerGamePacketListenerImpl) listener).processedDisconnect)) return; // CraftBukkit, MC-142590