Summary:
The detailed information widget isn't mirrored in RTL locales. This fix that.
It also use the Sunken shadow, which is not mirrored for RTL layouts. For now let's just
use Plain.

Reviewers: #kde_pim, mlaurent

Reviewed By: #kde_pim, mlaurent

Subscribers: #kde_pim

Tags: #kde_pim

Differential Revision: https://phabricator.kde.org/D9897