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

fixes https://gitlab.gnome.org/GNOME/gnome-tour/-/issues/45

- clean up unused pages
- add keyboard overview
- add search
- reword

Fixes https://gitlab.gnome.org/GNOME/gnome-tour/-/issues/41
Fixes https://gitlab.gnome.org/GNOME/gnome-tour/-/issues/42

tweak super key illustration

tweak super key illustration

- more of an adventure tour vibe

- avoid baloon duplicty

as the 'close' button is smaller, there's a weird
allocation thing when going from page 1 to page 2 for the first time

- make rocket more visible

- Fullcolor tour
- Basic CSS keyframe animations
- Use of default grey backgrounds due to headerbar

Fixes https://gitlab.gnome.org/GNOME/gnome-tour/-/issues/29

600x300px

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

- get rid of the purple. The joys of a colorblind designer

addresses concern https://gitlab.gnome.org/GNOME/gnome-tour/-/issues/17#note_886067

- align Software icon
- adjust grid position and alignment
- replace some app icons

See https://gitlab.gnome.org/GNOME/gnome-tour/-/issues/17

- Add dropshadow for the Software icon, replace Banner viewer with
  Foliate

Based on design review https://gitlab.gnome.org/GNOME/gnome-tour/-/issues/17

Provide a fun engaging closure to the guide.

Things left to do:

- adjust wording
- set background class to .last-page for the style to work

Fixes https://gitlab.gnome.org/GNOME/gnome-tour/issues/7

- scaled up all assets for them to render sharp
- unified the sizing so they don't jump around
- unified stroke sizes
- optimized with SVGO

original assets to create derivatives are at
https://gitlab.gnome.org/Teams/Design/os-mockups/tree/master/greeter/assets