Reparent systray icons to root window before restart/reload
Reparent systray icons to root window before restart/reload

And also ensure the systray's own window is killed when finalising.

This prevents them from being killed when the bar window, which they are
reparented to, is killed during `Bar.finalize()`.

Fixes #2909

qtile/qtile,qtile/qtile,ramnes/qtile,ramnes/qtile