Function start_hummock_workers 

pub fn start_hummock_workers(
    hummock_manager: HummockManagerRef,
    backup_manager: BackupManagerRef,
    meta_opts: &MetaOpts,
    get_pinned_snapshot_epochs: Box<dyn Fn() -> BoxFuture<'static, Option<HashMap<TableId, HashSet<u64>>>> + Send>,
) -> Vec<(JoinHandle<()>, Sender<()>)>

Start hummock’s asynchronous tasks.