With the surfaceless mode in the headless backend, it's now possible to
initiate the headless mode without any mode setting devices, or render
nodes, without any special CI runner privileges.
The native backend tests include screen cast tests, so make them
possible to run by starting pipewire. Testing shows that enabling audio
support (pulseaudio & jack compat layers) makes the tests dead lock and
eventually timeout, so disable those features for now.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1698>