Element Call ringing notifications (#2978)

- Add `ActiveCallManager` to handle incoming and ongoing calls.
- Add ringing call notifications with full screen intents and missed call ones as part of the 'conversation' notifications.

---------

Co-authored-by: ElementBot <benoitm+elementbot@element.io>

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/room/RustMatrixRoom.kt

@@ -596,6 +596,10 @@ class RustMatrixRoom(
         innerRoom.matrixToEventPermalink(eventId.value)
     }
 
+    override suspend fun sendCallNotificationIfNeeded(): Result<Unit> = runCatching {
+        innerRoom.sendCallNotificationIfNeeded()
+    }
+
     private fun createTimeline(
         timeline: InnerTimeline,
         isLive: Boolean,