Add game art as fallback for game switcher

[mohammadsyuhada]

Show boxart from .media folder as fallback in game switcher when no savestate preview exists.
Support multi-disk games in folders by checking parent folder for boxart

• A recent game with a savestate → should show savestate preview (unchanged)
• A recent game without savestate but with boxart → should show boxart centered with rounded corners
• A recent multi-disk game in folder without savestate → should show boxart from parent .media folder
• A recent a game without savestate and without boxart → should show "No Preview" (unchanged)

[mohammadsyuhada]

Same as this #131