prefs-dialog: Drop the notebook

Replaces the GtkNotebook by a HdyColumn in a GtkScrolledWindow, making
the preferences dialog a single long column. This also sets default a
height and width so the dialog isn't ridiculously small by default.

This allows the dialog to fit in narrow screens like on a phone.
3 jobs for wip/aplazas/adaptive-preferences in 13 minutes and 46 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Test
passed #201547
flatpak

00:11:25

 
  Deploy
passed #201548
review

00:02:20

manual #201549
allowed to fail manual
stop_review