[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/architecture/src/main/kotlin/io/element/android/libraries/architecture/Async.kt

@@ -57,3 +57,7 @@ suspend fun <T> (suspend () -> Result<T>).executeResult(state: MutableState<Asyn
         }
     )
 }
+
+fun <T> Async<T>.isLoading(): Boolean {
+    return this is Async.Loading<T>
+}