[wizard] Enable 1-finger touch scrolling

Summary:
Set a QScroller on the ListView

BUG: 406544

Test Plan:
Scrolling with touchpad: No change
Drag one finger on a touchscreen on the devicelist: List moves

Reviewers: #plasma, drosca, bshah

Reviewed By: bshah

Subscribers: bshah, ngraham, apol, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D21049