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/GridTile.test.tsx

@@ -26,7 +26,6 @@ import {
   createRingingMedia,
   type RingingMediaViewModel,
 } from "../state/media/RingingMediaViewModel";
-import { type MuteStates } from "../state/MuteStates";
 
 global.IntersectionObserver = class MockIntersectionObserver {
   public observe(): void {}
@@ -93,10 +92,8 @@ test("GridTile displays ringing media", async () => {
   >("ringing");
   const vm = createRingingMedia({
     pickupState$,
-    muteStates: {
-      video: { enabled$: constant(false) },
-    } as unknown as MuteStates,
     id: "test",
+    intent: "audio",
     userId: "@alice:example.org",
     displayName$: constant("Alice"),
     mxcAvatarUrl$: constant(undefined),