Ensure VillagerTrades doesn't load async - fixes #3495

In rare cases, this class could potentially be loaded from
the chunk threads causing it to initialize async and cause errors.

This would then break the server and chunk saving.

So ensure its loaded at start of server to avoid this.

Spigot-Server-Patches/Asynchronous-chunk-IO-and-loading.patch

@@ -2960,6 +2960,14 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
      }
  
      public String getServerIp() {
+@@ -0,0 +0,0 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
+                 dedicatedserver.setEraseCache(true);
+             }
+ 
++            Class.forName("net.minecraft.server.VillagerTrades");// Paper - load this sync so it won't fail later async
+             dedicatedserver.serverThread.setPriority(Thread.NORM_PRIORITY+2); // Paper - boost priority
+             dedicatedserver.serverThread.start();
+             // CraftBukkit end
 diff --git a/src/main/java/net/minecraft/server/NextTickListEntry.java b/src/main/java/net/minecraft/server/NextTickListEntry.java
 index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
 --- a/src/main/java/net/minecraft/server/NextTickListEntry.java