debian/55gnome-session_gnomerc: Make gnomerc works with both X11 and Wayland

The original 55gnome-session_gnomerc installed under the path /etc/X11/Xsession.d/ will only be executed with X11. To make both X11 and Wayland using it, the script can be moved into the folder /etc/profile.d/ and renamed as gnome-session_gnomerc. Besides, this patch also modifies the way to guard that it is GNOME (or GNOME-derived) session by checking the environment variable XDG_CURRENT_DESKTOP. The environment variable XDG_DATA_DIRS is manipulated as usual.