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/0811-Fix-demo-flag-not-enabling-demo-mode.patch

@@ -0,0 +1,22 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Warrior <50800980+Warriorrrr@users.noreply.github.com>
+Date: Fri, 7 Apr 2023 20:11:17 +0200
+Subject: [PATCH] Fix demo flag not enabling demo mode
+
+https://github.com/PaperMC/Paper/issues/9046
+
+diff --git a/src/main/java/net/minecraft/server/Main.java b/src/main/java/net/minecraft/server/Main.java
+index 13e1a914d4523f1c192db2a9a1ee6522e0ee27da..c33f85b570f159ab465b5a10a8044a81f2797f43 100644
+--- a/src/main/java/net/minecraft/server/Main.java
++++ b/src/main/java/net/minecraft/server/Main.java
+@@ -325,7 +325,9 @@ public class Main {
+ 
+                 /*
+                 dedicatedserver1.setPort((Integer) optionset.valueOf(optionspec11));
+-                dedicatedserver1.setDemo(optionset.has(optionspec2));
++                */
++                dedicatedserver1.setDemo(optionset.has("demo")); // Paper
++                /*
+                 dedicatedserver1.setId((String) optionset.valueOf(optionspec12));
+                 */
+                 boolean flag2 = !optionset.has("nogui") && !optionset.nonOptionArguments().contains("nogui");