Remove wall-time / unused skip tick protection (#11412)

Spigot still maintains some partial implementation of "tick skipping", a
practice in which the MinecraftServer.currentTick field is updated not
by an increment of one per actual tick, but instead set to
System.currentTimeMillis() / 50. This behaviour means that the tracked
tick may "skip" a tick value in case a previous tick took more than the
expected 50ms.

To compensate for this in important paths, spigot/craftbukkit
implements "wall-time". Instead of incrementing/decrementing ticks on
block entities/entities by one for each call to their tick() method,
they instead increment/decrement important values, like
an ItemEntity's age or pickupDelay, by the difference of
`currentTick - lastTick`, where `lastTick` is the value of
`currentTick` during the last tick() call.

These "fixes" however do not play nicely with minecraft's simulation
distance as entities/block entities implementing the above behaviour
would "catch up" their values when moving from a non-ticking chunk to a
ticking one as their `lastTick` value remains stuck on the last tick in
a ticking chunk and hence lead to a large "catch up" once ticked again.

Paper completely removes the "tick skipping" behaviour (See patch
"Further-improve-server-tick-loop"), making the above precautions
completely unnecessary, which also rids paper of the previous described
incompatibility with non-ticking chunks.

patches/server/0671-Fix-falling-block-spawn-methods.patch

@@ -0,0 +1,57 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Nassim Jahnke <nassim@njahnke.dev>
+Date: Fri, 4 Mar 2022 20:35:19 +0100
+Subject: [PATCH] Fix falling block spawn methods
+
+Restores the API behavior from previous versions of the server
+- Do not call API events
+- Do not replace the existing block in the world
+
+== AT ==
+public net.minecraft.world.entity.item.FallingBlockEntity <init>(Lnet/minecraft/world/level/Level;DDDLnet/minecraft/world/level/block/state/BlockState;)V
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+index 110a5d92d6154bc39c1916006a5cb74798092445..a1912eb5fd26898d7e9848ffb2052fce2fa10868 100644
+--- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
++++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+@@ -1393,7 +1393,12 @@ public class CraftWorld extends CraftRegionAccessor implements World {
+         Preconditions.checkArgument(material != null, "Material cannot be null");
+         Preconditions.checkArgument(material.isBlock(), "Material.%s must be a block", material);
+ 
+-        FallingBlockEntity entity = FallingBlockEntity.fall(this.world, BlockPos.containing(location.getX(), location.getY(), location.getZ()), CraftBlockType.bukkitToMinecraft(material).defaultBlockState(), SpawnReason.CUSTOM);
++        // Paper start - restore API behavior for spawning falling blocks
++        FallingBlockEntity entity = new FallingBlockEntity(this.world, location.getX(), location.getY(), location.getZ(), CraftBlockType.bukkitToMinecraft(material).defaultBlockState()); // Paper
++        entity.time = 1;
++
++        this.world.addFreshEntity(entity, SpawnReason.CUSTOM);
++        // Paper end - restore API behavior for spawning falling blocks
+         return (FallingBlock) entity.getBukkitEntity();
+     }
+ 
+@@ -1402,7 +1407,12 @@ public class CraftWorld extends CraftRegionAccessor implements World {
+         Preconditions.checkArgument(location != null, "Location cannot be null");
+         Preconditions.checkArgument(data != null, "BlockData cannot be null");
+ 
+-        FallingBlockEntity entity = FallingBlockEntity.fall(this.world, BlockPos.containing(location.getX(), location.getY(), location.getZ()), ((CraftBlockData) data).getState(), SpawnReason.CUSTOM);
++        // Paper start - restore API behavior for spawning falling blocks
++        FallingBlockEntity entity = new FallingBlockEntity(this.world, location.getX(), location.getY(), location.getZ(), ((CraftBlockData) data).getState());
++        entity.time = 1;
++
++        this.world.addFreshEntity(entity, SpawnReason.CUSTOM);
++        // Paper end - restore API behavior for spawning falling blocks
+         return (FallingBlock) entity.getBukkitEntity();
+     }
+ 
+diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntityTypes.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntityTypes.java
+index 481f0c62fcd4435d655cfe2f94f46262b24a7144..37527713b0afa6db19eefd57aaffcb2fe3544ce6 100644
+--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntityTypes.java
++++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntityTypes.java
+@@ -387,7 +387,7 @@ public final class CraftEntityTypes {
+         register(new EntityTypeData<>(EntityType.TNT, TNTPrimed.class, CraftTNTPrimed::new, spawnData -> new PrimedTnt(spawnData.minecraftWorld(), spawnData.x(), spawnData.y(), spawnData.z(), null)));
+         register(new EntityTypeData<>(EntityType.FALLING_BLOCK, FallingBlock.class, CraftFallingBlock::new, spawnData -> {
+             BlockPos pos = BlockPos.containing(spawnData.x(), spawnData.y(), spawnData.z());
+-            return FallingBlockEntity.fall(spawnData.minecraftWorld(), pos, spawnData.world().getBlockState(pos));
++            return new FallingBlockEntity(spawnData.minecraftWorld(), spawnData.x(), spawnData.y(), spawnData.z(), spawnData.world().getBlockState(pos)); // Paper - create falling block entities correctly
+         }));
+         register(new EntityTypeData<>(EntityType.FIREWORK_ROCKET, Firework.class, CraftFirework::new, spawnData -> new FireworkRocketEntity(spawnData.minecraftWorld(), spawnData.x(), spawnData.y(), spawnData.z(), net.minecraft.world.item.ItemStack.EMPTY)));
+         register(new EntityTypeData<>(EntityType.EVOKER_FANGS, EvokerFangs.class, CraftEvokerFangs::new, spawnData -> new net.minecraft.world.entity.projectile.EvokerFangs(spawnData.minecraftWorld(), spawnData.x(), spawnData.y(), spawnData.z(), (float) Math.toRadians(spawnData.yaw()), 0, null)));