feat: add status/metrics api

[lispc]

Request {
   task_query {
   start: timestamp, can be null,
   end: timestamp: can be null,
   tasks_limit: usize,
   }
}
Response {
    task_stats: {
        finished_task_num: usize,
        earliest_finished_tasks: vec[task_id] // len <= tasks_limit
        latest_finished_tasks: vec[task_id]
        processing_task_num: usize,
        earliest_processing_tasks: vec[task_id]
        latest_processing_tasks: vec[task_id]
        unstarted_task_num: usize,
        ...
        // any other types of tasks?
        // impl:   select task_status, count(*) from tasks group by task_status;
    },
    node_stats: {
         active_node_num: usize,
         offline_node_num: usize,
         total_node_num: usize,
     },
     proving_stats: {
           average_proving_time: float (secs) // last 100? or last hour? or [start, end) ? 
     }
}

[lispc]

maybe in the long run, promethus / grafana will be useful?

[lispc]

average total proving block/s and txp/s

[lispc]

current tps: 0.06.

4 cpu core.

( 300 tps needs 5000 cores )

Block(2, 5, 10, 5)