wayland: Add support for xx-fractional-scale-v2

The goal of this protocol is to address some current limitations with the logical coordinate system on Wayland when using fractional scaling.

Since the logical coordinate system has not enough resolution, it's possible to have gaps between maximized windows and panels or gaps between sub-surfaces. For example, with the current fractional scaling support, you may observe something like this

with the proposed protocol, it will look as expected

Some notes about the protocol: it is possible to re-phrase the problem. Specifically, by subdividing logical pixels. From the long term point of view, I think this approach is worth exploring. Especially if it could lead to a future where the logical coordinate system is uniform for all surfaces (realistically, not going to happen soon, but if we have a long term plan to simplify things, that'll be better). The changes that I speak won't be that different from the xx-fractional-scale-v2 (only change the types in a few places and perhaps rename some things), but in meanwhile, we need to have something so we can start experimenting with the overall idea of upscaling the logical coordinate system and see how it all goes.