Draft: AppMenu: port to standard XDG dbus annotation manager
This protocol is an upstreaming of the old_kde_kwin_appmenu and effectively replaces our propietary one.
No user-facing changes should be expected.
See: https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/52
Needs to implement:
- using client-wide menubars, but all of our infrastructure is built around the assumption that menubars 1:1 with windows
- maybe just use client-wide menubars as a "fallback" for clients w/o a menubar specified in said infrastructure?
Needs to discuss / notes:
- should the annotation manager be more clearly separated from the uses in application menu stuff?
- that would be more Logically Correct if code is being organized by wayland protocols, but not if code is being organized by functionality
- the annotations are only being used for application menu stuff currently, but that could change in the future
- it would make the diff substantially More to spin out the direct protocol stuff from the application menu manager
- while writing this i realised that i don't actually filter for the DBus interface and doing that would require having somewhere else to store "rejected" interfaces to noop them
- so i guess we do need to split that here