Instead of having different buttons or changing button behavior for making a PSBT, just have SendConfirmationDialog return whether the user wants a PSBT or a broadcasted transaction. Since this dialog is used by both the bumpFeeAction and the SendCoinsDialog, changes to both to support the different behavior is needed. They will check the return value of the SendConfirmationDialog for whether a PSBT needs to be created instead of checking whether private keys are disabled.
Strings used in this dialog are being slightly modified to work with both private keys enabled and disabled wallets.