This patch exposes a UI for choosing what happens when you left-click in the scrollbar
track in a Qt or KDE app. The default behavior is unchanged (left-click to page up/page
down) but now you can choose to warp the scroll handle straight to the clicked position.
Having this setting in the Workspace KCM opens the door to later making it also change
the behavior for GTK apps as well, allowing us to remove one more setting from the GTK
KCM and bringing us one step closer to finishing T10611: Set options for GTK apps in the respective KCMs.
Depends on D25360