feat(重构): 重构棋盘和棋子的逻辑

- 重构了 ChessBoard 和 ChessPiece 类的逻辑
- 添加了新版本的 ChineseChess 库
- 删除了旧版本的 VirtualBoard 和 VirtualPiece 类
- 更新了相关的场景和脚本

Scripts/Src/AbstractPiece.cs

@@ -0,0 +1,73 @@
+using System;
+using System.Collections.Generic;
+using Vector2I = Vector.Vector2I;
+
+public abstract class AbstractPiece : IPiece {
+    private Vector2I pos; // 注意这个坐标的非像素坐标而是棋盘坐标
+    private bool isSelected = false;
+    protected string name;
+    private Dictionary<string, object> data = new();
+
+    public Vector2I Pos {
+        get => pos;
+        set {
+            if (pos != value) {
+                var oldPos = pos;
+                pos = value;
+                OnPos?.Invoke(this, oldPos);
+            }
+        }
+    }
+
+    public bool IsSelected {
+        get => isSelected;
+        set {
+            if (isSelected != value) {
+                var oldIsSelected = isSelected;
+                isSelected = value;
+                OnSelected?.Invoke(this, oldIsSelected);
+            }
+        }
+    }
+
+    public string Name {
+        get => name;
+        set {
+            if (name != value) {
+                var oldName = name;
+                name = value;
+                OnName?.Invoke(this, oldName);
+            }
+        }
+    }
+
+    public Dictionary<string, object> Data {
+        get => data;
+        set => data = value;
+    }
+
+    public event EventHandler<Vector2I> OnPos;
+    public event EventHandler<Vector2I> OnMove;
+    public event EventHandler<bool> OnSelected;
+    public event EventHandler<string> OnName;
+
+    public virtual bool Move(Vector2I pos) {
+        if (!CanMove(pos)) {
+            return false;
+        }
+        Pos = pos;
+        OnMove?.Invoke(this, pos);
+        return true;
+    }
+
+    public abstract bool CanMove(Vector2I to);
+
+    public override string ToString() {
+        return $"{Name} at {pos}";
+    }
+
+    public AbstractPiece(string name = "", Vector2I pos = null) {
+        this.name = name;
+        this.pos = pos ?? new();
+    }
+}