[Room member list] Display room member list (#276)

* Implement room member list

* Move timeline initialization back to `TimelinePresenter`.

* Fix crash when the `innerRoom` inside a `RustMatrixRoom` is destroyed but `syncUpdateFlow` is still running.

* Address review comments

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/room/MatrixRoom.kt

@@ -31,9 +31,11 @@ interface MatrixRoom: Closeable {
     val alternativeAliases: List<String>
     val topic: String?
     val avatarUrl: String?
-    val members: List<RoomMember>
     val isEncrypted: Boolean
 
+    suspend fun members() : List<RoomMember>
+    suspend fun memberCount(): Int
+
     fun syncUpdateFlow(): Flow<Long>
 
     fun timeline(): MatrixTimeline