Function run 

pub(crate) async fn run(
    registry: Arc<Registry>,
    endpoint: Url,
    jwt: String,
    interval: Duration,
    external_labels: Vec<Label>,
    rate_limit_warned: Arc<AtomicBool>,
    telemetry_log_filter: Arc<String>,
    shutdown: Receiver<()>,
)

Run the periodic push loop until shutdown resolves, driving one final flush on the way out. Returns early if the HTTP client can’t be built.