[WIP DO NOT MERGE] qt: move backend setting to its own config

* this is totally a mess but builds, I just need to format and check everything
  im late to go work!
* prevents error on migration

Signed-off-by: Caio Oliveira <caiooliveirafarias0@gmail.com>

src/yuzu/main.cpp

@@ -4997,7 +4997,7 @@ int main(int argc, char* argv[]) {
     }
 
     // TODO: (DraVee) Un-alive the guy who wrote this
-    BackEndSettings::Restore();
+    BackEndSettings::Restore(); // lê backend_config.ini
     if (BackEndSettings::values.backend_force_x11.GetValue())
         qputenv("QT_QPA_PLATFORM", "xcb");