[wayland] Fix release of TabBox on Wayland

Summary:
The interaction is changed to trigger the check for release from the
TabBoxInputFilter instead of reacting on modifier changes. That way
it's possible to check for the relevant modifiers getting released
instead of getting all modifiers in. Also this means that the checks
are only performed when relevant.

BUG: 368590

Reviewers: KWin, Plasma on Wayland, bshah

Subscribers: plasma-devel, kwin

Tags: Plasma on Wayland, KWin

Differential Revision: https://phabricator.kde.org/D2773