Function toggle_saving_csv_tables 

pub(crate) async fn toggle_saving_csv_tables(
    start_saving: bool,
    expected_framerate_arc: Arc<RwLock<Option<f32>>>,
    output_base_dirname: PathBuf,
    braidz_write_tx_weak: WeakSender<SaveToDiskMsg>,
    per_cam_data_arc: Arc<RwLock<BTreeMap<RawCamName, PerCamSaveData>>>,
    shared_data: Arc<RwLock<ChangeTracker<BraidHttpApiSharedState>>>,
)