[DeviceNotifier] Port settings to QQC2 and Kirigami

Summary: Settings are ported to QtQuickControls 2 and now use a Kirigami Form Layout.

Test Plan:
Before:
{F6633459}
After:
{F6633461}

Reviewers: #vdg, #plasma, ngraham, davidedmundson

Reviewed By: #vdg, #plasma, ngraham, davidedmundson

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D19289