Space flow improvements. (#4430)

* Space flow improvements

- Use a state machine to select a space.
- Add a SpaceFlowCoordinator for recursively presenting subspaces.
- Get the spaceRoomListProxy when tapping on the space so we can indicate failures.
- Fix the total room count in SpaceListScreen.

* Refactor spaceRoom → spaceRoomProxy.

* Add a UI test for the Spaces flow.

ElementX/Sources/UITests/UITestsScreenIdentifier.swift

@@ -47,6 +47,7 @@ enum UITestsScreenIdentifier: String {
     case startChatWithSearchResults
     case userSessionScreen
     case userSessionScreenReply
+    case userSessionSpacesFlow
     case autoUpdatingTimeline
 }