Return cached room members before fetching new ones, do it in batches (#2274)

* Use cached users from the Rust SDK.

Also lazy load received users by batches.

* Create `RoomMemberListFetcher` to wrap all the room member loading logic

* Ensure we clear `RoomMember` Rust references if the fetching coroutine is canceled

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

@@ -75,7 +75,7 @@ interface MatrixRoom : Closeable {
     /**
      * Try to load the room members and update the membersFlow.
      */
-    suspend fun updateMembers(): Result<Unit>
+    suspend fun updateMembers()
 
     suspend fun updateRoomNotificationSettings(): Result<Unit>