Solitaire: Use a single State enum instead of a series of booleans

We had 4 different bools before, but the only valid states were either
that only one of them was true, or than none of them are true. An enum
is a better fit here, by enforcing that we can only be in one state at
a time.

Userland/Games/Solitaire/Game.h

@@ -204,11 +204,16 @@ private:
 
     bool m_mouse_down { false };
 
+    enum class State {
+        WaitingForNewGame,
+        NewGameAnimation,
+        GameInProgress,
+        StartGameOverAnimationNextFrame,
+        GameOverAnimation,
+    };
+    State m_state { State::WaitingForNewGame };
+
     Animation m_animation;
-    bool m_start_game_over_animation_next_frame { false };
-    bool m_game_over_animation { false };
-    bool m_waiting_for_new_game { true };
-    bool m_new_game_animation { false };
     uint8_t m_new_game_animation_pile { 0 };
     uint8_t m_new_game_animation_delay { 0 };