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.

1 files changed, 37 insertions, 0 deletions

diff --git a/patches/server/0423-Fix-sand-duping.patch b/patches/server/0423-Fix-sand-duping.patch
new file mode 100644
index 0000000000..5780d77de8
--- /dev/null
+++ b/patches/server/0423-Fix-sand-duping.patch
@@ -0,0 +1,37 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Spottedleaf <[email protected]>
+Date: Fri, 12 Jun 2020 13:33:19 -0700
+Subject: [PATCH] Fix sand duping
+
+If the falling block dies during teleportation (entity#move), then we need
+to detect that by placing a check after the move.
+
+diff --git a/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java b/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java
+index 18d81e8e8f387a7fb531652cb78c61a9bd5ae600..f6405e862b15b71dbb96215e604610fe5ff59bfc 100644
+--- a/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java
++++ b/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java
+@@ -126,6 +126,11 @@ public class FallingBlockEntity extends Entity {
+ 
+     @Override
+     public void tick() {
++        // Paper start - fix sand duping
++        if (this.isRemoved()) {
++            return;
++        }
++        // Paper end - fix sand duping
+         if (this.blockState.isAir()) {
+             this.discard();
+         } else {
+@@ -138,6 +143,12 @@ public class FallingBlockEntity extends Entity {
+ 
+             this.move(MoverType.SELF, this.getDeltaMovement());
+ 
++            // Paper start - fix sand duping
++            if (this.isRemoved()) {
++                return;
++            }
++            // Paper end - fix sand duping
++
+             // Paper start - Configurable EntityFallingBlock height nerf
+             if (this.level.paperConfig().fixes.fallingBlockHeightNerf != 0 && this.getY() > this.level.paperConfig().fixes.fallingBlockHeightNerf) {
+                 if (this.dropItem && this.level.getGameRules().getBoolean(GameRules.RULE_DOENTITYDROPS)) {