Please move to org.gnome.Calls on DBus
Reported by @guidog in https://source.puri.sm/Librem5/calls/-/issues/303
This is the bit blocking https://source.puri.sm/Librem5/calls/-/merge_requests/366 so we can have the DBus interface changes in one go. While at that it makes sense to switch UI files, desktop file, ... as well.