Better handling for forwarding key events to Wayland Server

A new protected method is added to InputEventFilter to forward a
QKeyEvent to the Wayland server. Several input filters need to forward
the event to have a proper state of the events. E.g. the TabBox filter,
but also the internal window filter and effects filter. It's important
to update all events even if the events are not forwarded to a surface.

This new method takes care of the general handling like ignoring key
repeats, etc.

Reviewed-By: bshah