[plasma-desktop] Add search ellipsis to Font Management and Date and Time

Summary: This patch adds an ellipsis to the filter and search labels in Font Management and Date and Time.

Reviewers: VDG, Plasma, ngraham

Reviewed By: VDG, ngraham

Subscribers: plasma-devel

Tags: Plasma

Maniphest Tasks: T10258

Differential Revision: https://phabricator.kde.org/D18047