Fix placement of chunk tracking - Fixes #1199

Spigot had code that returned early in chunk add/remove methods.

This was causing our code added to set current chunks and counts to
be skipped over if the entity was default not persistent but made persistent.

This was the source of many issues

Fixes #1208

Spigot-Server-Patches/Fix-Bugs-with-Spigot-Mob-Spawn-Logic.patch

@@ -14,7 +14,7 @@ Specially with servers using smaller mob spawn ranges than view distance, as wel
 This patch returns mob counting to use all loaded chunks, and 17x17 division.
 
 diff --git a/src/main/java/net/minecraft/server/Chunk.java b/src/main/java/net/minecraft/server/Chunk.java
-index e07ef14ed..aca1457b0 100644
+index da7b59434..1157bc7eb 100644
 --- a/src/main/java/net/minecraft/server/Chunk.java
 +++ b/src/main/java/net/minecraft/server/Chunk.java
 @@ -0,0 +0,0 @@ public class Chunk {
@@ -22,10 +22,11 @@ index e07ef14ed..aca1457b0 100644
          }
  
 -        this.entitySlices[i].remove(entity);
-+        if (!this.entitySlices[i].remove(entity)) { return; } // Paper
-         // Paper start - update counts
+         // Paper start
++        if (!this.entitySlices[i].remove(entity)) { return; }
+         entity.setCurrentChunk(null);
+         entityCounts.decrement(entity.entityKeyString);
          if (entity instanceof EntityItem) {
-             itemCounts[i]--;
 diff --git a/src/main/java/net/minecraft/server/SpawnerCreature.java b/src/main/java/net/minecraft/server/SpawnerCreature.java
 index 45a83ae99..ed22607d9 100644
 --- a/src/main/java/net/minecraft/server/SpawnerCreature.java