[FFe] UDI snap no longer strictly needed for WSL OOBE

[Carlos Nihelton]

Ubuntu Desktop Installer (UDI, for short) package implementing the WSL OOBE has been ported to Windows and the WSL application is able to launch the OOBE running as a native Win32 application, instead of relying on WSLg to display the OOBE.

That implies in the possibility of replacing UDI by Subiquity snap, which results in a smaller rootfs image (besides an enhanced experience due native rendering on graphics - instead of depending on RDP as it is currently with the OOBE running inside Ubuntu).

Fixing this would require:

- replace UDI by Subiquity snaps in the WSL seed;
- updating the wsl-setup package to the latest upstream (which is able to mount and launch Subiquity from its snap) LP: #1990426 .

Following the approach above won't have effects outside of WSL.

Kinetic being not an LTS is a good release to receive the fix for this first, as it affects a small audience of Ubuntu WSL community, giving us time to learn from them before backporting this to Jammy early next cycle.

[Łukasz Zemczak (sil2100)]

Same as the other one - a bit late, but let's go with it. Approved (since it's just a seed change).

[Brian Murray (brian-murray)]

commit 470c50d7c14f33623636f157d27c434fe5d2dedf
Author: Carlos Nihelton <email address hidden>
Date: Wed Sep 21 16:09:47 2022 -0300

    wsl: Replace ubuntu-desktop-installer by Subiquity snap LP: #1990526

    Also removes the gtk-themes snap required by UDI.
    That will result in a smaller rootfs.