debian/: add a session-migration script from utouch EDS extension

This let EDS sources migrate from eds-utouch extension to this one seemlessly, which is needed for Ubuntu Touch upgrade.

The session migration script is currently shipped in evolution-data- server-lomiri package, which hopefully is not pulled in as part of any cross-compilation dependency chain. If it is, we can separate the package later.

Use Ubuntu's pre-renamed variant of session-migraions package, because 1.) I don't want 2 variants of session-migrations on the image, and 2.) the current mtime workaround script [1] doesn't currently account for the post-renamed version.

[1]: https://gitlab.com/ubports/development/core/hybris-support/lxc-android-config/-/blob/main/usr/libexec/lxc-android-config/workaround-session-migration-mtime?ref_type=heads

Fixes: #1 (closed)