This removes Qt bug workarounds for a the old 6.5 we no longer use on
mobile.
This adds a new workaround for CHF as that somehow no longer has a
'symbol' set, so now we provide our own.
Also make sure we run a fetch when the user changes the currency.
In Qt5 the palette was introduced in the Control object (part of Qt-
Quick-Controls-2).
In Qt6 this property was moved to the superclass 'Item'.
This means that we no longer need to refer to a control when using a
palette, every single thing in QtQuick is an Item, afterall.
tomFlowee