Not possible to use inheritance for ChessPiece

[leesjensen]

The tests directly create a ChessPiece in TestUtilities.java. This makes it impossible for a student to implement inheritance as a solution for implementing the different chess pieces.

    public static ChessBoard loadBoard(String boardText) {
        var board = new ChessBoard();
        for (var c : boardText.toCharArray()) {
            switch (c) {
               // ...
                default -> {
                    ChessGame.TeamColor color = Character.isLowerCase(c) ? ChessGame.TeamColor.BLACK : ChessGame.TeamColor.WHITE;
                    var type = CHAR_TO_TYPE_MAP.get(Character.toLowerCase(c));
                    var position = new ChessPosition(row, column);
                    var piece = new ChessPiece(color, type);
                    board.addPiece(position, piece);
                    column++;
                }
            }
        }
    ```

Instead we could create a factory method on ChessPiece that `loadBoard` would call. 

We went away from the factory pattern a couple years ago. I'm not sure why that was and so we might run into a problem if we partially move back to it.