Add support to keyboard shortcuts inhibitor
Summary:
- Disable all global shortcuts
- For now don't disable spies (So opening menu with meta key is not disabled for now)
Depends on D29231
Test Plan: Tested with https://github.com/swaywm/wlroots/blob/master/examples/keyboard-shortcuts-inhibit.c
Reviewers: davidedmundson, zzag
Reviewed By: davidedmundson
Subscribers: romangg, broulik, apol, kwin
Tags: #kwin
Differential Revision: https://phabricator.kde.org/D29272