port Significantly improve performance of the end generation (#7919)

patches/server/0567-Add-sendOpLevel-API.patch

@@ -0,0 +1,51 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Mariell Hoversholm <proximyst@proximyst.com>
+Date: Tue, 29 Dec 2020 15:03:03 +0100
+Subject: [PATCH] Add sendOpLevel API
+
+
+diff --git a/src/main/java/net/minecraft/server/players/PlayerList.java b/src/main/java/net/minecraft/server/players/PlayerList.java
+index 6c7105af36339514db02800e651cd0948d48bdaf..42b2f5c61e2bd07c3c86d889949c5f24345680d6 100644
+--- a/src/main/java/net/minecraft/server/players/PlayerList.java
++++ b/src/main/java/net/minecraft/server/players/PlayerList.java
+@@ -1123,6 +1123,11 @@ public abstract class PlayerList {
+     }
+ 
+     private void sendPlayerPermissionLevel(ServerPlayer player, int permissionLevel) {
++        // Paper start - add recalculatePermissions parameter
++        this.sendPlayerPermissionLevel(player, permissionLevel, true);
++    }
++    public void sendPlayerPermissionLevel(ServerPlayer player, int permissionLevel, boolean recalculatePermissions) {
++        // Paper end
+         if (player.connection != null) {
+             byte b0;
+ 
+@@ -1137,8 +1142,10 @@ public abstract class PlayerList {
+             player.connection.send(new ClientboundEntityEventPacket(player, b0));
+         }
+ 
++        if (recalculatePermissions) { // Paper
+         player.getBukkitEntity().recalculatePermissions(); // CraftBukkit
+         this.server.getCommands().sendCommands(player);
++        } // Paper
+     }
+ 
+     public boolean isWhiteListed(GameProfile profile) {
+diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+index 23a92393036fea7631d7610b12d4e72fa6657203..fd6f948adb975f09b07ad7692c6a716616600ccc 100644
+--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
++++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+@@ -606,6 +606,13 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
+             ? (org.bukkit.entity.Firework) entity.getBukkitEntity()
+             : null;
+     }
++
++    @Override
++    public void sendOpLevel(byte level) {
++        Preconditions.checkArgument(level >= 0 && level <= 4, "Level must be within [0, 4]");
++
++        this.getHandle().getServer().getPlayerList().sendPlayerPermissionLevel(this.getHandle(), level, false);
++    }
+     // Paper end
+ 
+     @Override