Cleanup MCUtils patch for chunk system

Remove utilities that are unused, as well as replacing
the full chunk map with a concurrentutil implementation.

Additionally, fix the addition/removal of chunks to/from the
full chunk map so that getChunkIfLoaded correctly returns a
non-null chunk when calling the load or unload events.

patches/server/0738-Fix-plugin-loggers-on-server-shutdown.patch

@@ -37,7 +37,7 @@ index 0000000000000000000000000000000000000000..c1d3bac79bb8b4796c013ff4472f75dc
 +    }
 +}
 diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
-index 4b44447360b75b6dbe93d8176dcba2db02d77f1e..ba382397e39311598d044faf6b74665810d2e510 100644
+index 56ab40965ca6034ed430d4d5c4be99fa69a3a453..eef519384b5f8f6b2551ed61affe6cb1f3489702 100644
 --- a/src/main/java/net/minecraft/server/MinecraftServer.java
 +++ b/src/main/java/net/minecraft/server/MinecraftServer.java
 @@ -1239,6 +1239,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa