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.

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

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/room/FakeMatrixRoom.kt

@@ -86,6 +86,7 @@ class FakeMatrixRoom(
     override val liveTimeline: Timeline = FakeTimeline(),
     private var roomPermalinkResult: () -> Result<String> = { Result.success("room link") },
     private var eventPermalinkResult: (EventId) -> Result<String> = { Result.success("event link") },
+    var sendCallNotificationIfNeededResult: () -> Result<Unit> = { Result.success(Unit) },
     canRedactOwn: Boolean = false,
     canRedactOther: Boolean = false,
 ) : MatrixRoom {
@@ -528,6 +529,10 @@ class FakeMatrixRoom(
         theme: String?,
     ): Result<String> = generateWidgetWebViewUrlResult
 
+    override suspend fun sendCallNotificationIfNeeded(): Result<Unit> {
+        return sendCallNotificationIfNeededResult()
+    }
+
     override fun getWidgetDriver(widgetSettings: MatrixWidgetSettings): Result<MatrixWidgetDriver> = getWidgetDriverResult
 
     fun givenRoomMembersState(state: MatrixRoomMembersState) {