create TileStateInventoryHolder

a missing interface to centralize getSnapshotInventory methods

paper-api/src/main/java/io/papermc/paper/block/TileStateInventoryHolder.java

@@ -0,0 +1,39 @@
+package io.papermc.paper.block;
+
+import org.bukkit.block.TileState;
+import org.bukkit.inventory.BlockInventoryHolder;
+import org.bukkit.inventory.Inventory;
+import org.jspecify.annotations.NullMarked;
+
+/**
+ * Represents a {@link TileState} block that has an inventory.
+ */
+@NullMarked
+public interface TileStateInventoryHolder extends TileState, BlockInventoryHolder {
+
+    /**
+     * Gets the inventory of the block represented by this block state.
+     * <p>
+     * If the block was changed to a different type in the meantime, the
+     * returned inventory might no longer be valid.
+     * <p>
+     * If this block state is not placed this will return the captured inventory
+     * snapshot instead.
+     *
+     * @return the inventory
+     */
+    @Override
+    Inventory getInventory();
+
+    /**
+     * Gets the captured inventory snapshot of this container.
+     * <p>
+     * The returned inventory is not linked to any block. Any modifications to
+     * the returned inventory will not be applied to the block represented by
+     * this block state up until {@link #update(boolean, boolean)} has been
+     * called.
+     *
+     * @return the captured inventory snapshot
+     */
+    Inventory getSnapshotInventory();
+}