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.

1 files changed, 19 insertions, 0 deletions

diff --git a/patches/server/0614-Ensure-valid-vehicle-status.patch b/patches/server/0614-Ensure-valid-vehicle-status.patch
new file mode 100644
index 0000000000..f8ce44340d
--- /dev/null
+++ b/patches/server/0614-Ensure-valid-vehicle-status.patch
@@ -0,0 +1,19 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Nassim Jahnke <[email protected]>
+Date: Tue, 28 Sep 2021 09:47:47 +0200
+Subject: [PATCH] Ensure valid vehicle status
+
+
+diff --git a/src/main/java/net/minecraft/server/level/ServerPlayer.java b/src/main/java/net/minecraft/server/level/ServerPlayer.java
+index 6648af4d8d795637fae444dc85803b399592fd7d..25ca370c0b19eca529fc2c980c50e899013f0897 100644
+--- a/src/main/java/net/minecraft/server/level/ServerPlayer.java
++++ b/src/main/java/net/minecraft/server/level/ServerPlayer.java
+@@ -574,7 +574,7 @@ public class ServerPlayer extends net.minecraft.world.entity.player.Player {
+             }
+         }
+ 
+-        if (persistVehicle && entity1 != null && entity != this && entity.hasExactlyOnePlayerPassenger()) {
++        if (persistVehicle && entity1 != null && entity != this && entity.hasExactlyOnePlayerPassenger() && !entity.isRemoved()) { // Paper - Ensure valid vehicle status
+             // CraftBukkit end
+             CompoundTag nbttagcompound2 = new CompoundTag();
+             CompoundTag nbttagcompound3 = new CompoundTag();