Make const data members non-const

As recommended by C++ Core Guidelines C.12.

Plugin and Game are still non-copy-constructable or assignable due to
having members that are non-copy-constructable/assignable, but
consistency is still good.

include/loot/exception/cyclic_interaction_error.h

@@ -54,7 +54,7 @@ public:
   LOOT_API std::vector<Vertex> GetCycle();
 
 private:
-  const std::vector<Vertex> cycle_;
+  std::vector<Vertex> cycle_;
 };
 }
 

include/loot/exception/undefined_group_error.h

@@ -50,7 +50,7 @@ public:
   LOOT_API std::string GetGroupName() { return groupName_; }
 
 private:
-  const std::string groupName_;
+  std::string groupName_;
 };
 }
 

src/api/game/game.h

@@ -81,8 +81,8 @@ public:
 private:
   void CacheArchives();
 
-  const GameType type_;
-  const std::filesystem::path gamePath_;
+  GameType type_;
+  std::filesystem::path gamePath_;
 
   GameCache cache_;
   LoadOrderHandler loadOrderHandler_;

src/api/plugin.h

@@ -84,7 +84,7 @@ private:
                            const std::filesystem::path& pluginPath);
   static unsigned int GetEspluginGameId(GameType gameType);
 
-  const std::string name_;
+  std::string name_;
   std::unique_ptr<::Plugin, decltype(&esp_plugin_free)> esPlugin;
   bool isEmpty_;  // Does the plugin contain any records other than the TES4
                   // header?