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/0621-prevent-unintended-light-block-manipulation.patch

@@ -0,0 +1,25 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Jake Potrebic <jake.m.potrebic@gmail.com>
+Date: Mon, 13 Sep 2021 18:55:45 -0700
+Subject: [PATCH] prevent unintended light block manipulation
+
+
+diff --git a/src/main/java/net/minecraft/world/level/block/LightBlock.java b/src/main/java/net/minecraft/world/level/block/LightBlock.java
+index 01722473a4861533dba0ab6edf3982c0278c41e1..2b3c395529a15c9f07a4c0cff7f82199298bcb6d 100644
+--- a/src/main/java/net/minecraft/world/level/block/LightBlock.java
++++ b/src/main/java/net/minecraft/world/level/block/LightBlock.java
+@@ -49,6 +49,14 @@ public class LightBlock extends Block implements SimpleWaterloggedBlock {
+         builder.add(LEVEL, WATERLOGGED);
+     }
+ 
++    // Paper start - prevent unintended light block manipulation
++    @Override
++    protected net.minecraft.world.ItemInteractionResult useItemOn(final ItemStack stack, final BlockState state, final Level world, final BlockPos pos, final Player player, final net.minecraft.world.InteractionHand hand, final BlockHitResult hit) {
++        if (player.getItemInHand(hand).getItem() != Items.LIGHT || !player.mayInteract(world, pos) || !player.mayUseItemAt(pos, hit.getDirection(), player.getItemInHand(hand))) { return net.minecraft.world.ItemInteractionResult.SKIP_DEFAULT_BLOCK_INTERACTION; } // Paper - Prevent unintended light block manipulation
++        return super.useItemOn(stack, state, world, pos, player, hand, hit);
++    }
++    // Paper end - prevent unintended light block manipulation
++
+     @Override
+     protected InteractionResult useWithoutItem(BlockState state, Level world, BlockPos pos, Player player, BlockHitResult hit) {
+         if (!world.isClientSide && player.canUseGameMasterBlocks()) {