Revert "Block: Get rid of state bitmasks"

This reverts commit b7b05e729e.

Apparently this was premature, because we still need these things to deal with default state remapping.

src/pocketmine/block/SnowLayer.php

@@ -50,6 +50,10 @@ class SnowLayer extends Flowable implements Fallable{
 		$this->layers = BlockDataValidator::readBoundedInt("layers", $stateMeta + 1, 1, 8);
 	}
 
+	public function getStateBitmask() : int{
+		return 0b111;
+	}
+
 	public function canBeReplaced() : bool{
 		return $this->layers < 8;
 	}