Rewrite chunk system (#8177)

Patch documentation to come

Issues with the old system that are fixed now:
- World generation does not scale with cpu cores effectively.
- Relies on the main thread for scheduling and maintaining chunk state, dropping chunk load/generate rates at lower tps.
- Unreliable prioritisation of chunk gen/load calls that block the main thread.
- Shutdown logic is utterly unreliable, as it has to wait for all chunks to unload - is it guaranteed that the chunk system is in a state on shutdown that it can reliably do this? Watchdog shutdown also typically failed due to thread checks, which is now resolved.
- Saving of data is not unified (i.e can save chunk data without saving entity data, poses problems for desync if shutdown is really abnormal.
- Entities are not loaded with chunks. This caused quite a bit of headache for Chunk#getEntities API, but now the new chunk system loads entities with chunks so that they are ready whenever the chunk loads in. Effectively brings the behavior back to 1.16 era, but still storing entities in their own separate regionfiles.

The above list is not complete. The patch documentation will complete it.

New chunk system hard relies on starlight and dataconverter, and most importantly the new concurrent utilities in ConcurrentUtil.

Some of the old async chunk i/o interface (i.e the old file io thread reroutes _some_ calls to the new file io thread) is kept for plugin compat reasons. It will be removed in the next major version of minecraft.

The old legacy chunk system patches have been moved to the removed folder in case we need them again.

patches/server/0126-String-based-Action-Bar-API.patch

@@ -1,58 +0,0 @@
-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
-From: Aikar <aikar@aikar.co>
-Date: Tue, 27 Dec 2016 15:02:42 -0500
-Subject: [PATCH] String based Action Bar API
-
-
-diff --git a/src/main/java/net/minecraft/network/protocol/game/ClientboundSetActionBarTextPacket.java b/src/main/java/net/minecraft/network/protocol/game/ClientboundSetActionBarTextPacket.java
-index 32ef3edebe94a2014168b7e438752a80b2687e5f..ab6c58eed6707ab7b0aa3e7549a871ad7dfad87f 100644
---- a/src/main/java/net/minecraft/network/protocol/game/ClientboundSetActionBarTextPacket.java
-+++ b/src/main/java/net/minecraft/network/protocol/game/ClientboundSetActionBarTextPacket.java
-@@ -7,6 +7,7 @@ import net.minecraft.network.protocol.Packet;
- public class ClientboundSetActionBarTextPacket implements Packet<ClientGamePacketListener> {
-     private final Component text;
-     public net.kyori.adventure.text.Component adventure$text; // Paper
-+    public net.md_5.bungee.api.chat.BaseComponent[] components; // Paper
- 
-     public ClientboundSetActionBarTextPacket(Component message) {
-         this.text = message;
-@@ -21,6 +22,8 @@ public class ClientboundSetActionBarTextPacket implements Packet<ClientGamePacke
-         // Paper start
-         if (this.adventure$text != null) {
-             buf.writeComponent(this.adventure$text);
-+        } else if (this.components != null) {
-+            buf.writeComponent(this.components);
-         } else
-         // Paper end
-         buf.writeComponent(this.text);
-diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
-index 72b1429c4976b8db13d2185486c240b2fadb4ea9..538db39d365252a63d578728b362a8dde3e8838e 100644
---- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
-+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
-@@ -280,6 +280,26 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
-     }
- 
-     // Paper start
-+    @Override
-+    public void sendActionBar(BaseComponent[] message) {
-+        if (getHandle().connection == null) return;
-+        net.minecraft.network.protocol.game.ClientboundSetActionBarTextPacket packet = new net.minecraft.network.protocol.game.ClientboundSetActionBarTextPacket((net.minecraft.network.chat.Component) null);
-+        packet.components = message;
-+        getHandle().connection.send(packet);
-+    }
-+
-+    @Override
-+    public void sendActionBar(String message) {
-+        if (getHandle().connection == null || message == null || message.isEmpty()) return;
-+        getHandle().connection.send(new net.minecraft.network.protocol.game.ClientboundSetActionBarTextPacket(CraftChatMessage.fromStringOrNull(message)));
-+    }
-+
-+    @Override
-+    public void sendActionBar(char alternateChar, String message) {
-+        if (message == null || message.isEmpty()) return;
-+        sendActionBar(org.bukkit.ChatColor.translateAlternateColorCodes(alternateChar, message));
-+    }
-+
-     @Override
-     public void setPlayerListHeaderFooter(BaseComponent[] header, BaseComponent[] footer) {
-          if (header != null) {