[sddm-theme] Apply new username prompt and user list icons

Summary: This patch applies the icons added in D19020 to the Breeze SDDM theme.

Test Plan:
Before

After

Reviewers: VDG, Plasma, ngraham, filipf

Reviewed By: VDG, ngraham, filipf

Subscribers: filipf, plasma-devel

Tags: Plasma

Maniphest Tasks: T10325

Differential Revision: https://phabricator.kde.org/D19129