Improve internal model of ringing, expose ringing intent to call UI

I found our code's internal model of ringing a little overgrown (it had superfluous states like 'unknown') and difficult to extend with metadata or callbacks relating to ring attempts. By modeling ringing instead as a stream of ring attempts, where each attempt has an intent, a recipient, and an eventual outcome (accept/decline/timeout), I find it more natural to work with.

This makes room for a future 'try again' callback to allow ringing someone again after a timeout, and also forced me to look for a simpler solution to the duplicate leave sound effects. I exposed the intent of the ringing attempt to the call UI so I can later use it in the header.

src/tile/SpotlightTile.tsx

@@ -212,7 +212,6 @@ const SpotlightRingingMediaItem: FC<SpotlightRingingMediaItemProps> = ({
 }) => {
   const { t } = useTranslation();
   const pickupState = useBehavior(vm.pickupState$);
-  const videoEnabled = useBehavior(vm.videoEnabled$);
 
   return (
     <MediaView
@@ -222,7 +221,8 @@ const SpotlightRingingMediaItem: FC<SpotlightRingingMediaItemProps> = ({
         pickupState === "ringing"
           ? {
               text: t("video_tile.calling"),
-              Icon: videoEnabled ? VideoCallSolidIcon : VoiceCallSolidIcon,
+              Icon:
+                vm.intent === "video" ? VideoCallSolidIcon : VoiceCallSolidIcon,
             }
           : { text: t("video_tile.call_ended"), Icon: EndCallIcon }
       }