Implement wp-fractional-scale-v1

This will allow clients to render at native resolution on wayland when fractional scaling is used.

Some challenges of how we handle logical sizes being integers over the wire for resizing and such remain.

Draft as it depends on wayland-protocols to land, which depends on us having a tested MR ready. Also unit tests.

Relevant implementatons: Qt5: https://invent.kde.org/davidedmundson/qtwayland/-/tree/work/d_ed/fractional_scale_backport Qt6: https://codereview.qt-project.org/c/qt/qtwayland/+/420041 SDL: https://github.com/libsdl-org/SDL/pull/5906