Set complete vectors instead of creting them at runtime

Summary: I tested a bit of code with -02 to measure the speed gains of using a std::initializer_list over appending to a temporary and appending to temporary is around 50% slower, so I removed all the code that appened to temporaries for a initializer list in breeze.

Reviewers: Breeze, Plasma, davidedmundson

Reviewed By: Plasma, davidedmundson

Subscribers: davidedmundson, ngraham, zzag, plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D13591