gdk/wayland: Switch behavior of BTN_STYLUS/STYLUS2 as middle/right click

gdk/wayland: Switch behavior of BTN_STYLUS/STYLUS2 as middle/right click

This mapping of stylus evdev input event codes into GDK button numbers
makes gdk/wayland inconsistent with gdk/x11, so depending on the backend
the same button middle-click pastes or right-click pops up menus.

Make the wayland backend consistent with X11, so that a GNOME wayland
session gets these buttons consistently mapped across all kinds of
clients.

(cherry-picked from commit e28ff79bec53ecd56885390ba4a66019cde598c6)

Forwarded: https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/6169
Origin: 3.24.39, commit:e205bdaa89342bb1d47527be0cdfbc1bfb0f5f59

Gbp-Pq: Name gdk-wayland-Switch-behavior-of-BTN_STYLUS-STYLUS2-as-midd.patch