Game specific configs (#3376)

* poc

* Set up variable game specific variable copies

* Set up getters to return the game specific option if it exists

* Avoid exceptions if a value isn't in the config

* Make sure the custom configs folder exists

* Update + review comments + rewrite

* The loathsome clang-formatter

* Specify which getter/setter is used everywhere

src/common/config.h

@@ -16,7 +16,7 @@ struct GameInstallDir {
 
 enum HideCursorState : int { Never, Idle, Always };
 
-void load(const std::filesystem::path& path);
+void load(const std::filesystem::path& path, bool is_game_specific = false);
 void save(const std::filesystem::path& path);
 
 int getVolumeSlider();