We've had a few warnings sticking around for unused pieces
of code, or things that needed some form of error handling.

This commit upgrades our rust dependencies and ports
Tour to libadwaita+GTK4. As part of porting we now use
GtkPicture instead of GtkImage, and AdwClamps to hold pages
in place.

This port is part of https://gitlab.gnome.org/GNOME/Initiatives/-/issues/26 and handles https://gitlab.gnome.org/GNOME/Initiatives/-/issues/32

Fixes https://gitlab.gnome.org/GNOME/gnome-tour/-/issues/36

As per glib docs: `set_application_name`: Sets a human-readable name for the application.
This name should be localized if possible, and is intended for display to the user.

you should be able to configure the video path at build
time by passing --video_path=absolute_path
which will be played instead of displaying the LOGO