Improve the Saddle API for Horses

Not all horses with Saddles have armor. This lets us break up the horses with saddles
and access their saddle state separately from an interface shared with Armor.

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftAbstractHorse.java

@@ -5,6 +5,7 @@ import java.util.UUID;
 import net.minecraft.world.entity.ai.attributes.Attributes;
 import org.bukkit.craftbukkit.CraftServer;
 import org.bukkit.craftbukkit.inventory.CraftInventoryAbstractHorse;
+import org.bukkit.craftbukkit.inventory.CraftSaddledInventory;
 import org.bukkit.entity.AbstractHorse;
 import org.bukkit.entity.AnimalTamer;
 import org.bukkit.entity.Horse;
@@ -107,6 +108,6 @@ public abstract class CraftAbstractHorse extends CraftAnimals implements Abstrac
 
     @Override
     public AbstractHorseInventory getInventory() {
-        return new CraftInventoryAbstractHorse(this.getHandle().inventory);
+        return new CraftSaddledInventory(getHandle().inventory);
     }
 }