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/0364-Fix-CraftScheduler-runTaskTimerAsynchronously-Plugin.patch

@@ -0,0 +1,21 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: ossi <oser0002@gmail.com>
+Date: Fri, 12 Jun 2020 01:38:06 +0300
+Subject: [PATCH] Fix CraftScheduler#runTaskTimerAsynchronously(Plugin,
+ Consumer<BukkitTask>, long, long) scheduling a non-repeating task instead of
+ a repeating one.
+
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java b/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java
+index 02835e4f0a0b262af27acff0939c981cae728db4..d7c2d8993a172e343669228cf24a58d8992a1c10 100644
+--- a/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java
++++ b/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java
+@@ -197,7 +197,7 @@ public class CraftScheduler implements BukkitScheduler {
+ 
+     @Override
+     public void runTaskTimerAsynchronously(Plugin plugin, Consumer<? super BukkitTask> task, long delay, long period) throws IllegalArgumentException {
+-        this.runTaskTimerAsynchronously(plugin, (Object) task, delay, CraftTask.NO_REPEATING);
++        this.runTaskTimerAsynchronously(plugin, (Object) task, delay, period); // Paper
+     }
+ 
+     @Override