Current Chunk for Entity and Block Entities, counts by entity type

This enables us a fast reference to the entities current chunk instead
of having to look it up by hashmap lookups.

We also store counts by type to further enable other performance optimizations in later patches.

Spigot-Server-Patches/Configurable-Chunk-Inhabited-Timer.patch

@@ -23,7 +23,7 @@ index e634c3afd..54f23ea75 100644
 +    }
  }
 diff --git a/src/main/java/net/minecraft/server/Chunk.java b/src/main/java/net/minecraft/server/Chunk.java
-index 172d00bdc..300a56191 100644
+index bf3b64e37..6b13e1d7d 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 {