Make osk-wayland obsolete

squeekboard 1.20.0-2 from Debian will use update-alternatives to manage
the /u/s/a/sm.puri.OSK0.desktop finally allowing us to obsolete
osk-wayland here.

We do so by making sm.puri.OSK0-legacy.desktop use update-alternatives
too and giving it a lower priority than squeekboards.

As older squeekboard in PureOS Byzantium doesn't worry about
sm.puri.OSK0 at all so an update of librem5-base-defaults won't change
anything for the user.

We can drop sm.puri.OSK0-legacy and osk-wayland for Crimson

debian/librem5-base-defaults.alternatives

+Name: Phosh-OSK
+Link: /usr/share/applications/sm.puri.OSK0.desktop
+Alternative: /usr/share/applications/sm.puri.OSK0-legacy.desktop
+Priority: 20

debian/librem5-base-defaults.install

@@ -8,7 +8,7 @@ default/audio/profile-sets           usr/share/pulseaudio/alsa-mixer/
 default/audio/ucm2                   usr/share/alsa/
 default/audio/alsa-restore.service.d lib/systemd/system/
 
-default/sm.puri.OSK0.desktop         usr/share/applications/
+default/sm.puri.OSK0-legacy.desktop         usr/share/applications/
 default/osk-wayland                  usr/bin/
 
 # librem5 specific environment variables

default/sm.puri.OSK0.desktop → default/sm.puri.OSK0-legacy.desktop

 [Desktop Entry]
 Type=Application
 Name=On-screen keyboard
-Comment=Default on-screen keyboard
+Comment=Legacy on-screen keyboard wrapper
 Exec=/usr/bin/osk-wayland
 Categories=GNOME;Core;
 OnlyShowIn=GNOME;