Block: get rid of getNonPersistentStateBitmask(), add writeStateToItemMeta()

this is more flexible and less confusing.

src/block/Dirt.php

@@ -41,12 +41,12 @@ class Dirt extends Opaque{
 		return $this->coarse ? BlockLegacyMetadata::DIRT_FLAG_COARSE : 0;
 	}
 
-	public function getStateBitmask() : int{
-		return 0b1;
+	protected function writeStateToItemMeta() : int{
+		return $this->writeStateToMeta();
 	}
 
-	public function getNonPersistentStateBitmask() : int{
-		return 0;
+	public function getStateBitmask() : int{
+		return 0b1;
 	}
 
 	public function isCoarse() : bool{ return $this->coarse; }