Don't use automatic font sizing for text on pie chart faces

Instead, use the new maximumLength function from Formatter to determine
the maximum size of text and if that is too small, use the "small" font
instead. Finally, if even that does not fit, completely hide the text.

BUG: 437276
2 jobs for !164 with work/ahiemstra/popupsize in 3 minutes and 4 seconds (queued for 22 minutes and 30 seconds)
latest merge request