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/Further-improve-server-tick-loop.patch

@@ -105,9 +105,9 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
                  long i;
  
 @@ -0,0 +0,0 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
+                     }
                  }
                  // Spigot start
-                 ++MinecraftServer.currentTickLong; // Paper - track current tick as a long
 -                if ( tickCount++ % MinecraftServer.SAMPLE_INTERVAL == 0 )
 -                {
 -                    long curTime = Util.getMillis();