Clean up hierarchy of rails

detector rail has fundamentally different functionality than activator and powered rails, so it's misleading to present the same APIs for both.
detector rail's 'powered' state is better referred to as 'activated', since it means the detector rail is actually _producing_ power, and not _receiving_ power.

src/block/DetectorRail.php

@@ -23,7 +23,29 @@ declare(strict_types=1);
 
 namespace pocketmine\block;
 
-class DetectorRail extends RedstoneRail{
+class DetectorRail extends BaseRail{
+	protected bool $activated = false;
+
+	public function isActivated() : bool{ return $this->activated; }
+
+	/** @return $this */
+	public function setActivated(bool $activated) : self{
+		$this->activated = $activated;
+		return $this;
+	}
+
+	protected function writeStateToMeta() : int{
+		return parent::writeStateToMeta() | ($this->activated ? BlockLegacyMetadata::REDSTONE_RAIL_FLAG_POWERED : 0);
+	}
+
+	public function readStateFromData(int $id, int $stateMeta) : void{
+		parent::readStateFromData($id, $stateMeta);
+		$this->activated = ($stateMeta & BlockLegacyMetadata::REDSTONE_RAIL_FLAG_POWERED) !== 0;
+	}
+
+	protected function getConnectionsFromMeta(int $meta) : ?array{
+		return self::CONNECTIONS[$meta & ~BlockLegacyMetadata::REDSTONE_RAIL_FLAG_POWERED] ?? null;
+	}
 
 	//TODO
 }