Port Kirigami Plasma plugin Units to use a C++ implementation
This ports the units to C++, which is required from 5.86.
I was unsure about the behaviour of devicePixelRatio and related things, right now the Kirigami class assumes we are using Qt scaling. I do not know if this plugin needs to support Plasma's own scaling.
The "desktop" variant was dropped since the qqc2-desktop-style plugin already does the exact same.
Edited by Arjen Hiemstra