wayland: Don't raise window when entering fullscreen mode

If the window is inactive and it enters fullscreen mode for some reason,
it can create a situation where keyboard goes to a window occluded by
the fullscreen window.

This change makes XdgToplevelClient::setFullScreen() not raise the
window. It's the responsibility of whoever requested the fullscreen mode
change.

If the configure event is acknowledged, the window's stack layer will be
invalidated and recomputed. If the window is active, it will be promoted
to the ActiveLayer, otherwise its stack position won't change.