Add method to access owner

Makes handling ISpecialInventory ownership much more consistent with a lot less spaghetti.

internal/v1_16_R3/src/main/java/com/lishid/openinv/internal/v1_16_R3/SpecialEnderChest.java

@@ -80,6 +80,11 @@ public class SpecialEnderChest extends InventoryEnderChest implements ISpecialEn
         }
     }
 
+    @Override
+    public @NotNull Player getPlayer() {
+        return owner.getBukkitEntity();
+    }
+
     @Override
     public void update() {
         this.owner.getEnderChest().update();

internal/v1_16_R3/src/main/java/com/lishid/openinv/internal/v1_16_R3/SpecialPlayerInventory.java

@@ -212,6 +212,11 @@ public class SpecialPlayerInventory extends PlayerInventory implements ISpecialP
         this.playerOnline = false;
     }
 
+    @Override
+    public @NotNull HumanEntity getPlayer() {
+        return this.player.getBukkitEntity();
+    }
+
     @Override
     public ItemStack splitStack(int i, final int j) {
         List<ItemStack> list = this.items;