Fixes #32

This reverts commit be014fca

See https://gitlab.gnome.org/GNOME/gnome-build-meta/-/merge_requests/1498#note_1367023

It is no longer used and if we ever re-add it, we can think of another way
to do that.

This is in preparation for a future gtk-rs release

Because of an API change in libadwaita,
we need to use the latest version of
libadwaita-rs.

Temporarily bundles libadwaita, as the nightly
SDK doesn't have a new enough libadwaita because
we block the build.

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

Anyhow was only used for paginator and
Option makes arguably more sense here than Result

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

this also glib::get_os_info which requires glib >2.64
closes #10

Would love to keep using gtk4, but we can't get it into 3.36 otherwise.