[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

{F6621998}
{F6621997}

After

{F6621999}

{F6622000}

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