Change CommandAllKey to Meta
Summary: Alt + Left Click to move windows has a tendency to conflict with creative workflow apps. While Alt can be changed to Meta in KWin's settings, Alt + Left Click shortcuts often cannot be customized in apps. Rather than making every user who runs into this problem change their settings, we should change our default settings to improve KWin's default usability.
This change also makes CommandAllKey comply with the XDG Global Shortcuts spec: https://gitlab.freedesktop.org/xdg/xdg-specs/-/blob/master/global-shortcuts/global-shortcuts-spec.md
Test Plan: The relevant parts of the relevant tests pass. kwin-testInternalWindow fails, but for unrelated reasons that have something to do with XWayland.