x11: Fix shrinking window size after toggling no border multiple times

The first move() in X11Client::createDecoration() will alter the client
size, which will result in the subsequent resize() incorrectly resizing
to a smaller window size.

In order to fix that issue, this change makes X11Client adjust the
frame geometry atomically after creating or destroying window decoration.

BUG: 449988


(cherry picked from commit 8e057326)