Remember the last folder when adding assets and app icons

Remember the last folder used when adding image assets or choosing application icons, so repeated selections do not require navigating from the home directory each time.

Keep separate remembered folders for image assets and application icons. All icon artwork selections should share the icon folder, including default artwork and individual sizes. Remember these folders for the current Studio session; reopening an editor should retain the remembered location, while restarting Studio may return to the platform's default location.

This makes repeated imports easier, especially when supplying several size-specific app icons. No additional setting should be needed.