Block Replacer on chunk load

This modification provides the ability to automatically replace blocks from one mod with blocks from another mod when chunks are loaded. This is especially useful in situations where pack developers want to replace one mod with another while preserving already placed blocks in the world.

Key feature: the system works even in cases where the original mod has already been removed from the pack. The only condition is that the chunk must not have been resaved after the mod was removed. This makes the replacement process as smooth and safe as possible for the game world.