Bug#1076096: gnome-session: Split Xorg session to separate binary package

[Jeremy Bícha]

Source: gnome-session
Version: 46.0-3
Tags: trixie

I think we should offer a gnome-session-xsession package to allow for
users to easily opt in or out of having a GNOME Xorg session
available.

The binary name matches Fedora's gnome-session-xsession which
surprisingly has existed since 2008, long before gnome-session
supported Wayland.

Note that this is completely unrelated to the idea of
- building GNOME Shell without XWayland support (no plans to do that)
- making it impossible to log into GNOME on Xorg (this has been
proposed in GNOME but will not happen at least in Debian before Debian
Trixie is released)

Thank you,
Jeremy Bícha