Block: Clean up internal constructor inconsistencies

I don't dare look how big this commit is or how many bugs it introduced...

src/pocketmine/block/PumpkinStem.php

@@ -23,18 +23,8 @@ declare(strict_types=1);
 
 namespace pocketmine\block;
 
-use pocketmine\item\Item;
-
 class PumpkinStem extends Stem{
 
-	protected $id = self::PUMPKIN_STEM;
-
-	protected $itemId = Item::PUMPKIN_SEEDS;
-
-	public function getName() : string{
-		return "Pumpkin Stem";
-	}
-
 	protected function getPlant() : Block{
 		return BlockFactory::get(Block::PUMPKIN);
 	}