Consider dropping the GtkWidget::scale property
Maintaining this property properly requires us to keep track of too many things:
- the display
- the surface
- the monitor
The propagation of scale changes is awkwardly mixed up with css state changes.
Only few widgets actually need to care about scale changes:
- GtkImage to reload icons at the new scale
- Text is not affected, since the scale only gets applied when glyphs are put in the glyph cache, which happens in the gsk renderer