Allow to control the group separator and the minus sign for numerica values.
This is a follow up for the request on https://discuss.kde.org/t/more-settings-for-number-formatting/13846.
Similarly to how we allow to control the decimal separator we need to allow to control the appearance of the group separator.
As to the minus sign (more information about this subject in https://jakubmarian.com/hyphen-minus-en-dash-and-em-dash-difference-and-usage-in-english/), it's seems to be available in QLocale https://codebrowser.dev/qt5/qtbase/src/corelib/text/qlocale_p.h.html#QSystemLocale::NegativeSign but I don't see how to control it now.