chore: unsingletonize UserDataController (#5459)

The `user-data.json` file will save immediately on change, and on exit
(on dtor) if necessary. So we don't need to manually call save

src/Application.hpp

@@ -160,7 +160,7 @@ private:
     std::unique_ptr<TwitchIrcServer> twitch;
     FfzBadges *const ffzBadges{};
     SeventvBadges *const seventvBadges{};
-    UserDataController *const userData{};
+    std::unique_ptr<UserDataController> userData;
     ISoundController *const sound{};
     TwitchLiveController *const twitchLiveController{};
     std::unique_ptr<PubSub> twitchPubSub;