collect the runtime statistics for operators in the coprocessor

[zz-jason]

Feature Request

Describe the feature you'd like:

At present, TiDB has supported the explain analyze statement to show the runtime statistics about the query execution, for example:

TiDB(root@127.0.0.1:test) > explain analyze select sum(b) from t group by a;
+----------------------+----------+------+--------------------------------------------------------------------+----------------------------------+
| id                   | count    | task | operator info                                                      | execution info                   |
+----------------------+----------+------+--------------------------------------------------------------------+----------------------------------+
| StreamAgg_9          | 8000.00  | root | group by:group_0, funcs:sum(sum_0)                                 | time:399.086µs, loops:4, rows:3  |
| └─IndexLookUp_20     | 10000.00 | root |                                                                    | time:382.873µs, loops:4, rows:3  |
|   ├─IndexScan_18     | 10000.00 | cop  | table:t, index:a, range:[NULL,+inf], keep order:true, stats:pseudo |                                  |
|   └─TableScan_19     | 10000.00 | cop  | table:t, keep order:false, stats:pseudo                            |                                  |
+----------------------+----------+------+--------------------------------------------------------------------+----------------------------------+
4 rows in set (0.00 sec)

It would be more useful if we can show the runtime statistics of the operators implemented and executed in the TiKV coprocessor.

Describe alternatives you've considered: No

Teachability, Documentation, Adoption, Migration Strategy: No

[zz-jason]

related to this issue: https://github.com/pingcap/tidb/issues/8213