[binary-clock] Port configuration window to QQC2 and Kirigami.FormLayout

Summary: This patch ports binary-clock's configuration window to QQC2 and Kirigami.FormLayout.

Test Plan:
Before:
{F6682645}

After:
{F6682649}

Reviewers: #vdg, #plasma, ngraham

Reviewed By: #vdg, ngraham

Subscribers: abetts, ngraham, plasma-devel

Tags: #plasma

Maniphest Tasks: T10586

Differential Revision: https://phabricator.kde.org/D19669