Grid Inventory (#21931)

* Grid Inventory

* oh boy we keep cracking on

* auto insertion is kinda working? gross, too!

* pieces and proper layouts

* fix the sprites

* mousing over grid pieces... finally

* dragging deez nuts all over the screen

* eek!

* dragging is 90% less horrendous

* auto-rotating

* flatten

* Rotation at last

* fix rotation and change keybind for removing items.

* rebinding and keybinding

* wow! look at that! configurable with a button! cool!

* dragging is a bit cooler, eh?

* hover insert, my beloved

* add some grids for storage, fix 1x1 storages, fix multiple inputs at once

* el navigation

* oh yeah some stuff i forgor

* more fixes and QOL stuff

* the griddening

* the last of it (yippee)

* sloth review :)

Content.Shared/Storage/ItemStorageLocation.cs

@@ -0,0 +1,40 @@
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.Storage;
+
+[DataDefinition, Serializable, NetSerializable]
+public partial record struct ItemStorageLocation
+{
+    /// <summary>
+    /// The rotation, stored a cardinal direction in order to reduce rounding errors.
+    /// </summary>
+    [DataField]
+    private Direction _rotation;
+
+    /// <summary>
+    /// The rotation of the piece in storage.
+    /// </summary>
+    public Angle Rotation
+    {
+        get => _rotation.ToAngle();
+        set => _rotation = value.GetCardinalDir();
+    }
+
+    /// <summary>
+    /// Where the item is located in storage.
+    /// </summary>
+    [DataField]
+    public Vector2i Position;
+
+    public ItemStorageLocation(Angle rotation, Vector2i position)
+    {
+        Rotation = rotation;
+        Position = position;
+    }
+
+    public bool Equals(ItemStorageLocation? other)
+    {
+        return Rotation == other?.Rotation &&
+               Position == other.Value.Position;
+    }
+};