Currently, we don't handle too well the removal of a MetaWaylandEventInterface
during meta_wayland_event_interface_invalidate_all_focus(), since the
MetaWaylandEventInterface may be freed at an intermediate point in that function
while handling the focus change for all input devices.
Turn this invalidate_all_focus() function into a MetaWaylandInput method, and
always ensure to use the currently effective MetaWaylandEventInterface when
resetting the focus for each device.
This fixes the situation through handling reentrancy naturally, a focus
sync (say, triggered by a grab) would reset a device focus (say, pointer), which
would remove an event interface (say, a pointer constraint), which would
invalidate_all_focus() again underneath using the new effective
MetaWaylandEventInterface. When that is done, the initial invalidate_all_focus()
call would re-apply the same focus to the same currently effective
MetaWaylandEventInterface, resulting in a no-op for the remainder of the function.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3618>
1d5676bc9a