We currently consider idle nodes as in use to avoid too fast state
changes and thus flickering of the indicator icon. However, the current
idle timeout is rather long and arguably confusing for users.
Thus switch to only consider running nodes as in use, but delay
disabling of the indicator by 500ms.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2854>
Pipewire allows us to easily track whether any cameras are in used by
checking the state of camera nodes. Add a simple camera monitor to the
shell, allowing us to show e.g. a status indicator.
Naturally the monitor is limited to apps using Pipewire for camera
access and thus subject to the same chicken-egg problem like the camera
portal - it could confuse users that apps may use the camera without
being noticed by the monitor. The hope and assumption here is that a
better shell integration might speed up adoption of the new camera APIs
Pipewire 0.3.49 is required for refcounted `pw_init()`/`pw_deinit()`.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2840>
