Add the JoinRoomScreen into the SpaceFlowCoordinator. (#4513)

* Add the JoinRoomScreen into the SpaceFlowCoordinator.

The screen needs further work to make the join work.

* Fix the tests completing the join flow with the right action.

ElementX/Sources/Services/Spaces/SpaceRoomListProxyProtocol.swift

@@ -8,6 +8,10 @@
 import Combine
 import MatrixRustSDK
 
+enum SpaceRoomListProxyError: Error {
+    case missingSpace
+}
+
 // sourcery: AutoMockable
 protocol SpaceRoomListProxyProtocol {
     var spaceRoomProxy: SpaceRoomProxyProtocol { get }