Disable use of Locks on main thread for DataPaletteBlock

This should greatly improve performance by using a No Op lock
while on the main thread.

Vanilla always had a write lock on write operations, but we added
a Read Lock during Async Chunks to make concurrent writes non fatal
for Async Chunks.

This means we added on a bunch of over head to all chunk read operations.

This corrects that, as well as disabling the write lock while on main thread.

It is a general rule that you do not touch a chunk async once it is loaded
into the world, as we never had locks on the chunk before 1.13 even.

So once we are on main, we don't expect concurrent access to begin with,
so we don't need the write locks either.

Spigot-Server-Patches/Fix-Sending-Chunks-to-Client.patch

@@ -14,7 +14,7 @@ This fix always sends chunks to the client, and simply updates
 the client anytime post processing is triggered with the new chunk data.
 
 diff --git a/src/main/java/net/minecraft/server/Chunk.java b/src/main/java/net/minecraft/server/Chunk.java
-index 83df52f30..0b0a5424e 100644
+index 8da88e1c3a..64cec6d692 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 implements IChunkAccess {
@@ -41,7 +41,7 @@ index 83df52f30..0b0a5424e 100644
      }
  
 diff --git a/src/main/java/net/minecraft/server/PlayerChunk.java b/src/main/java/net/minecraft/server/PlayerChunk.java
-index 04ad94e17..748d5f28e 100644
+index 04ad94e171..748d5f28e5 100644
 --- a/src/main/java/net/minecraft/server/PlayerChunk.java
 +++ b/src/main/java/net/minecraft/server/PlayerChunk.java
 @@ -0,0 +0,0 @@ public class PlayerChunk {