Backup restoration fixes

XXMessengerClient

• Update MessengerRestoreBackup function, so it does not try to clean up storage on failure.

xx-messenger example

• Save restored contact when restoring from backup.
• Destory messenger when restoring backup fails.

Examples/xx-messenger/Sources/RestoreFeature/RestoreFeature.swift

@@ -141,6 +141,7 @@ public let restoreReducer = Reducer<RestoreState, RestoreAction, RestoreEnvironm
         ))
         return .success(.finished)
       } catch {
+        try? env.messenger.destroy()
         return .success(.failed(error as NSError))
       }
     }