[Game] Refactor subtype tally code to be more generic (#7021)

* [Game] Refactor subtype tally code to be more generic

* remove default case

* consolidate empty check

* fix include guard

* backwards compatibility with qt5

cockatrice/src/game_graphics/tally/tally.h

@@ -0,0 +1,40 @@
+#ifndef COCKATRICE_TALLY_H
+#define COCKATRICE_TALLY_H
+#include <QString>
+
+class CardItem;
+
+/** @brief A single row of the tally output. */
+struct TallyRow
+{
+    QString name;  ///< The row name (displayed on the left)
+    QString value; ///< Value for the row (displayed on the right)
+
+    bool operator==(const TallyRow &) const = default;
+};
+
+/**
+ * The tally type
+ */
+enum class TallyType
+{
+    None,
+    Subtypes,
+};
+
+namespace Tally
+{
+
+/**
+ * @brief Analyzes the selected cards according to the tally type and builds the resulting tally rows.
+ * This forwards the cards to the code for that tally type.
+ *
+ * @param cards The list of selected card items to analyze.
+ * @param type The type of tally to do
+ * @return Rows sorted in top-to-bottom display order
+ */
+QList<TallyRow> compute(const QList<CardItem *> &cards, TallyType type);
+
+} // namespace Tally
+
+#endif // COCKATRICE_TALLY_H