CalendarHeaderModel does not update when locale changes

There is an issue with QML calendar when we switch the locale from one language to another with different firstDayOWeek the column header display is remaining static as per the first locale selected.

I've attached a simple QML app to demonstrate the bug. The attached app displays the calendar in French on startup. In French, the first day of the week is Monday ( ie., lun. in French ). When the locale is switched to English in the combobox, observe that the days model gets updated.

But the column header which displays the weekday remains static causing Monday to be displayed as the first day of the week. Feb 3rd,2019 is displayed as Monday instead of Sunday.

The month header in the calendar control gets initialized only once in Component.onCompleted of https://github.com/qt/qtquickcontrols/blob/bd952e904070d8eb07748d620829e9dadb8022ba/src/controls/Private/CalendarHeaderModel.qml#L92