This now uses libadwaita for everything, but will need some updates when
libadwaita 1.2 is released. Avatars are currently non-functional as the existing
buddy icon API leaves a lot to be desired and doesn't work for what we're trying
to do here.

Created new accounts with the new dialog.
Modified accounts with the new dialog.
Modified accounts with the old dialog and verified the changes showed up in the old dialog.
Created accounts with the old dialog and verified they were displayed properly by the new dialog.