Units: add iconSizeForLabelsRoundedUp
The current iconSizeForLabels rounds QFontMetrics::height down to the nearest supported icon size, but sometimes a component looks nicer if the icon is actually larger than the text (e.g. a ToolButton).
Specifically this is added for qqc2-breeze-style's ToolButton and ItemDelegate.
Also add iconSizeForLabelsRoundedDown and make iconSizeForLabels an alias of this. Should probably deprecate it too, but idk how to do that.