Create a `CommandDataRetrieval` abstraction, use it for the current `UpadateNodeData` command and for the new command used in `SavingsDataProvider` (remove direct api calls from this place)

Because there are direct API calls in SavingsDataProvider, it is possible to crash the TUI on the Savings screen because of CommunicationError (which should be suppressed by exception handlers in Commands class).

Also when new Providers are created soon, this will be a bigger problem