Change AnnouncePlayerPlay to announce speed 0 for pausing slideshow or picture

because for picture/slideshow, it currently announce OnPlay with speed 1, it doesn't make sense, so I suggest change the speed to 0 for standalone picture or pausing slideshow.

although we can announce OnPause for that, but it's not unify since normally we use OnStart/OnStop pair. then a startup OnPause or OnPlay with speed 0, which should we use?