Summary:
alternative approach: try to resize the winidow to make room for the keyboard.
the new input wayland protocol doesn't have anymore the overlap rectangle (and it would not be going to work with qwidget apps anyways)

in the future will probably be needed anextension to the input protocol v3 which partially gets back this, tough window resizing is needed regardless

what's missing: the resize should be "temporary" and the window should be restored to its previous geometry when the keyboard closes

Test Plan: tested with test QML code

Reviewers: #plasma, #kwin, bshah, graesslin, romangg, davidedmundson

Reviewed By: #plasma, #kwin, romangg, davidedmundson

Subscribers: nicolasfella, mart, kwin, davidedmundson, graesslin

Tags: #kwin

Maniphest Tasks: T9815

Differential Revision: https://phabricator.kde.org/D18818