[4.8.x] gdk/x11: Reset all scroll valuators on enter
From: @carlosg
We no longer need to make much distinction between multiple logical devices, plus it breaks esp. with the Xwayland input device distribution. Just iterate across all devices and reset their scroll valuators.
Closes: #4160 (closed)
(cherry picked from commit 824e9833)
Fixes #4160 (closed) and its duplicate #5202 (closed), aka https://bugs.debian.org/1029972 and https://bugs.launchpad.net/ubuntu/+source/gtk4/+bug/1993594, in the 4.8.x branch.