The autosave refactoring that was done in
7adad5aaf5831dc5adcee140f38aacc4a5db2518 used g_engine for identifying the
autosave slot. This worked for in-game save/load, but doesn't fit when
called from the launcher.
Fix by passing MetaEngine to SaveStateDescriptor ctor and using it for this
query.
Amends 7adad5aaf5831dc5adcee140f38aacc4a5db2518.
For each engine:
- Make a new folder detection
- Move detection-related files inside the folder
- Add a new module "enginename/detection"
- Add DETECT_OBJS here
- Adjust the normal engine module to remove detect_objs
- Adjust every file for the new changes.
