Qt: Refresh view on wallet options widget shown #fixes 1838

[dnchk]

Refresh view when wallet options widget is shown, so that changes applied in debug console are visible in the widget.

[furszy]

Hello, thanks for the contributions, adding some missing context to this and a possible solution.

The issue is the split threshold set from the RPC command that is not notifying the options model to update the split threshold data specific row (without it, there is no view update triggered for the widget/view connected to it). The wallet option widget doesn't need to poll for the data at every show (nor refresh the entire options data set which triggers the view update for every other option data listener as well).

As the RPC commands don't have access to the options model, a good solution to this would be:
(1) create a new stakeSplitChanged signal in the wallet.
(2) subscribe to the signal inside the options model.
(3) broadcast the signal from the RPC setstakesplitthreshold command (encapsulated inside a wallet method).
(4) update the specific row from the options model signal handler (using Q_EMIT dataChanged(index, index) where the index row number is OptionsID::StakeSplitThreshold and column is probably 0)

[random-zebra]

Fixed within #2293