wayland: Fix xdg-toplevel and xdg-popup window initialization

Buggy clients can commit the wl_surface several times in a row. On the
other hand, XdgToplevelInterface and XdgPopupInterface consider a
surface to be initialized if it has been configured. If the second
wl_surface commit comes before the configure event is sent, kwin will
initialize a toplevel or popup twice, which can trigger asserts.

BUG: 466530
(cherry picked from commit 43cac750)