Fix duplicate toasts appearing for the same call if two events appear. (#31693)

* fix export

* Don't allow duplicate toasts.

* fix imports

* fix

* fix rel_type to be m.reference in tests

* Fix case where redactions were not longer checked.

* Ensure toastkey is calculated by the room call_id

* Ensure we fetch the call event if it does not exist locally.

* cleanup / reduce code complexity

* Add docs

* Add comment

* merge condition

playwright/e2e/voip/element-call.spec.ts

@@ -74,7 +74,7 @@ async function sendRTCState(bot: Bot, roomId: string, notification?: "ring" | "n
         },
         "m.relates_to": {
             event_id: resp.event_id,
-            rel_type: "org.matrix.msc4075.rtc.notification.parent",
+            rel_type: "m.reference",
         },
         "m.call.intent": intent,
         "notification_type": notification,