Add shortcuts as default shortcuts

Summary:
Add the shortcuts a the default shortcuts to the actionCollection()
When resetting to the default shortcuts this no longers clears them.
BUG: 401244

Test Plan: Open yakuake and confige shortcuts. Hit the "Defaults" button. The shortcuts should no longer be cleared.

Reviewers: hein

Reviewed By: hein

Differential Revision: https://phabricator.kde.org/D18500