test(nix): share the wallpaper scenario, and the files kfw must sync

Wallpapers and the colors of the borders that come from them are in the
config of both ports. wallpaper.run is the neutral part: a monitor's
wallpaper at start, a workspace's own while it is shown, the ring in the
hue of the wallpaper, and a changed wallpaper put back. Platform gets
put_file, wallpaper and set_wallpaper; in a Plasma session restart_with
restarts the module's unit with the user's komorebi.json. The KDE extra
keeps what only the shell tells. sync-e2e-core carries the two fakes the
shared tests import.

scripts/sync-e2e-core

@@ -20,7 +20,7 @@ dest=${1:?usage: sync-e2e-core [--check] DEST}
 repo=$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)
 lib=$repo/nix/tests/vm/lib
 
-tests=(fake_platform.py test_checks.py test_suite.py test_pixels.py test_snapshot.py test_recorded.py test_tiling.py
+tests=(fake_platform.py fake_strip.py fake_wallpaper.py test_checks.py test_suite.py test_pixels.py test_snapshot.py test_recorded.py test_tiling.py
   test_focus_moving.py)
 
 status=0