Make Watchdog thread extend TickThread

This allows the watchdog thread to be seen as the
primary thread during shutdown, which prevents it
from tripping thread checks in various areas.

Fixes #12030

paper-server/src/main/java/org/spigotmc/WatchdogThread.java

@@ -11,7 +11,7 @@
 import org.bukkit.Bukkit;
 import org.bukkit.craftbukkit.CraftServer;
 
-public class WatchdogThread extends Thread {
+public class WatchdogThread extends ca.spottedleaf.moonrise.common.util.TickThread { // Paper - rewrite chunk system
 
     public static final boolean DISABLE_WATCHDOG = Boolean.getBoolean("disable.watchdog"); // Paper - Improved watchdog support
     private static WatchdogThread instance;