Function run_watcher 

async fn run_watcher<R: Runtime>(
    runtime: R,
    rx: FileEventReceiver,
    sighup_stream: impl Stream<Item = ()> + Unpin,
    weak_mgr: Weak<CfgMgr<R>>,
    debounce_interval: Option<Duration>,
) -> Result<()>

Start watching for configuration changes.

Spawned from UnlaunchedWatcher::launch.