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, 28 insertions, 0 deletions

diff --git a/patches/server/0497-Reduce-blockpos-allocation-from-pathfinding.patch b/patches/server/0497-Reduce-blockpos-allocation-from-pathfinding.patch
new file mode 100644
index 0000000000..a6a02f3817
--- /dev/null
+++ b/patches/server/0497-Reduce-blockpos-allocation-from-pathfinding.patch
@@ -0,0 +1,28 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Spottedleaf <[email protected]>
+Date: Sat, 25 Apr 2020 17:10:55 -0700
+Subject: [PATCH] Reduce blockpos allocation from pathfinding
+
+
+diff --git a/src/main/java/net/minecraft/world/level/pathfinder/WalkNodeEvaluator.java b/src/main/java/net/minecraft/world/level/pathfinder/WalkNodeEvaluator.java
+index c48e097464977dbec22d1370c3393ba1fe105137..ede91a2fbe67480d2b6bcdeb776f87da0b69bdae 100644
+--- a/src/main/java/net/minecraft/world/level/pathfinder/WalkNodeEvaluator.java
++++ b/src/main/java/net/minecraft/world/level/pathfinder/WalkNodeEvaluator.java
+@@ -495,7 +495,7 @@ public class WalkNodeEvaluator extends NodeEvaluator {
+                             return BlockPathTypes.DANGER_FIRE;
+                         }
+ 
+-                        if (world.getFluidState(pos).is(FluidTags.WATER)) {
++                        if (blockState.getFluidState().is(FluidTags.WATER)) {
+                             return BlockPathTypes.WATER_BORDER;
+                         }
+                         } // Paper
+@@ -526,7 +526,7 @@ public class WalkNodeEvaluator extends NodeEvaluator {
+             } else if (blockState.is(Blocks.COCOA)) {
+                 return BlockPathTypes.COCOA;
+             } else {
+-                FluidState fluidState = world.getFluidState(pos);
++                FluidState fluidState = blockState.getFluidState(); // Paper - remove another get type call
+                 if (fluidState.is(FluidTags.LAVA)) {
+                     return BlockPathTypes.LAVA;
+                 } else if (isBurningBlock(blockState)) {