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/0261-Improve-Server-Thread-Pool-and-Thread-Priorities.patch

@@ -92,10 +92,10 @@ index 54562fa04d14a937451ea7aa9d80194f2c31b471..4cf88f6d815d60cfbf8e4ecf9d96d0cf
          return executorService;
      }
 diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
-index 5d429b707383e6620a0d83f23d7a8694ecc70735..995ee6b2af01a14d61a031008dd05518668a98ae 100644
+index 2d5ae71c143556a938f078d2fb84cab7bd4f789b..f3f3f80f14bc1df13b80033aa143fcccab6f3a31 100644
 --- a/src/main/java/net/minecraft/server/MinecraftServer.java
 +++ b/src/main/java/net/minecraft/server/MinecraftServer.java
-@@ -323,6 +323,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
+@@ -322,6 +322,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
          thread.setUncaughtExceptionHandler((thread1, throwable) -> {
              MinecraftServer.LOGGER.error("Uncaught exception in server thread", throwable);
          });