perf: process 16 chunks/player/tick on dedicated server, revert async save

Chunk loading now batches up to 16 nearest-first requests per player per
tick on dedicated server (client stays at 1), improving tick recovery
time after player join.

Reverts the async save system -- the background thread snapshot/compress
path added complexity without measurable benefit. Autosave on Windows64
server now uses the standard synchronous flush like client, in
preparation for a proper async implementation from upstream.

Minecraft.World/ConsoleSaveFileOriginal.h

@@ -77,11 +77,6 @@ public:
 	virtual void LockSaveAccess();
 	virtual void ReleaseSaveAccess();
 
-#ifdef _WINDOWS64
-	// Called from the main thread to commit a completed async save to StorageManager.
-	static void CommitPendingAsyncSave();
-#endif
-
 	virtual ESavePlatform getSavePlatform();
 	virtual bool isSaveEndianDifferent();
 	virtual void setLocalPlatform();