Return a list of connected controllers.

Return an absolute path to the PNG image glyph for the provided digital action name. The current action set in use for the controller will be used for the lookup. You should cache the result and maintain your own list of loaded PNG assets.

You shouldn't really need to call this because it get called by RunCallbacks on SteamClient but Valve think it might be a nice idea if you call it right before you get input info - just to make sure the info you're getting is 100% up to date.