Bookkeeper: Toggle display of fiat values in balance sheet and sats flow

[evansmj]

Given I have toggled the fiat value radio button / checkbox (design tbd),
And I have my fiat currency selected in the settings menu,
When I am viewing the balance sheet or sats flow chart,
Then I should see the y-axis for both charts use the selected fiat values and the balance sheet table should show fiat values using my selected fiat value, and the hover tooltip should also display fiat value.

When I have toggled the Sats or BTC setting in Settings,
Then I should see either sats or btc value in both y-axises, the balance sheet table, and in the tool-tips for balance sheet, sats flow, and volume chart.

[evansmj]

implemented by @ShahanaFarooqui