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/0450-Additional-Block-Material-API.patch

@@ -0,0 +1,40 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Wed, 30 Dec 2020 19:43:01 -0500
+Subject: [PATCH] Additional Block Material API
+
+Faster version for isSolid() that utilizes NMS's state for isSolid instead of the slower
+process to do this in the Bukkit API
+
+Adds API for buildable, replaceable, burnable too.
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java b/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
+index aa644231425b9622437538b5c092d4064a40cced..98e87dc15e2ed23f6897ba6359846ff5bc32b655 100644
+--- a/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
++++ b/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
+@@ -440,6 +440,25 @@ public class CraftBlock implements Block {
+         return this.getNMS().liquid();
+     }
+ 
++    // Paper start
++    @Override
++    public boolean isBuildable() {
++        return this.getNMS().isSolid(); // This is in fact isSolid, despite the fact that isSolid below returns blocksMotion
++    }
++    @Override
++    public boolean isBurnable() {
++        return this.getNMS().ignitedByLava();
++    }
++    @Override
++    public boolean isReplaceable() {
++        return this.getNMS().canBeReplaced();
++    }
++    @Override
++    public boolean isSolid() {
++        return this.getNMS().blocksMotion();
++    }
++    // Paper end
++
+     @Override
+     public PistonMoveReaction getPistonMoveReaction() {
+         return PistonMoveReaction.getById(this.getNMS().getPistonPushReaction().ordinal());