Implement setInverseShortcutActions D-Bus method and config storage

Depends on new API proposed for KGlobalAccel 6.26.

In terms of storage, this persists the action pairs in a sub-group of the component called "InverseActions", e.g. [kwin][$InverseAction] for the "kwin" component. We do not currently store which of the actions is "forward" and which is "backward", if we need this we can add it at a later time.

---

Here's what my kglobalshortcutsrc looks like after applying this and kwin!9100:

[kwin]
Activate Window Demanding Attention=Meta+Ctrl+A,Meta+Ctrl+A,Activate Window Demanding Attention
ClearLastMouseMark=Meta+Shift+F12,Meta+Shift+F12,Clear Last Mouse Mark
ClearMouseMarks=Meta+Shift+F11,Meta+Shift+F11,Clear Mouse Marks
Cycle Overview=none,none,Cycle through Overview and Grid View
Cycle Overview Opposite=none,none,Cycle through Grid View and Overview
Decrease Opacity=none,,Decrease Opacity of Active Window by 5%
(...)

[kwin][$InverseAction]
Cycle Overview=Cycle Overview Opposite
Increase Opacity=Decrease Opacity
MoveZoomRight=MoveZoomLeft
MoveZoomUp=MoveZoomDown
Switch One Desktop Up=Switch One Desktop Down
Switch One Desktop to the Left=Switch One Desktop to the Right
Switch Window Left=Switch Window Right
Switch Window Up=Switch Window Down
Switch to Next Screen=Switch to Previous Screen
Switch to Previous Desktop=Switch to Next Desktop
Switch to Screen Below=Switch to Screen Above
Switch to Screen to the Left=Switch to Screen to the Right
Walk Through Windows=Optional,Walk Through Windows (Reverse)
Walk Through Windows Alternative (Reverse)=Optional,Walk Through Windows Alternative
Walk Through Windows of Current Application (Reverse)=Optional,Walk Through Windows of Current Application
Walk Through Windows of Current Application Alternative=Optional,Walk Through Windows of Current Application Alternative (Reverse)
Window Grow Vertical=Window Shrink Vertical
Window Lower=Window Raise
Window One Desktop Down=Window One Desktop Up
Window One Desktop to the Left=Window One Desktop to the Right
Window One Screen Down=Window One Screen Up
Window One Screen to the Right=Window One Screen to the Left
Window Pack Down=Window Pack Up
Window Pack Left=Window Pack Right
Window Shrink Horizontal=Window Grow Horizontal
Window to Next Desktop=Window to Previous Desktop
Window to Next Screen=Window to Previous Screen
view_zoom_in=view_zoom_out