wayland: Add request focus support via gtk_shell

wayland: Add request focus support via gtk_shell

A gtk_surface.present request was added to gtk_surface which takes
timestamp from some input event, and uses that timestamp to figure out
whether the window can be presented or not. If we don't have a
timestamp, we should just give up instead of making up our own,
otherwise we might steal someones focus.

https://bugzilla.gnome.org/show_bug.cgi?id=763037