Align z's to pixel grid in system.svg

Summary: This does the same thing as D20586, but for the Breeze desktop theme. The diff shows a lot of changes because I optimized the SVG.

Test Plan: Looks exactly the same as D20586

Reviewers: VDG, ngraham

Reviewed By: VDG, ngraham

Subscribers: kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D20597