Update wl_compositor protocol support

[Saviq]

In particular, we're behind with wl-compositor v4. The field is at v6

Originally posted by @AlanGriffiths in #3803

@Saviq

https://gitlab.freedesktop.org/wayland/wayland/-/commit/9afab91d212164b56c7eefd234c798fc59ae3fd8

https://gitlab.freedesktop.org/wayland/wayland/-/commit/fceabb7e9e167e1100c244bb4f460c8a346a5478

Ah but this isn't just about wl_compositor..

Still, looks like we're after wl_surface.offset and wl_surface.preferred_buffer_scale, don't seem like a huge deal?

Offset is effectively moving the same from .attach, and scale we should be easy to work with.

And actually would improve zooming, that we're planning.

@AlanGriffiths

Yeah, that seems the bulk of it. And desirable. There's likely significant plumbing needed to join stuff up