add cpu usage in hot region statistics and TIDB_HOT_REGIONS_HISTORY

[nolouch]

Feature Request

Describe your feature request related problem

To retrieve the top N tables ranked by QUERY_RATE in a query, you can use ORDER BY to sort by QUERY_RATE and combine it with LIMIT to restrict the number of records returned. Here is the revised SQL query:

SELECT DB_NAME, TABLE_NAME, AVG(QUERY_RATE) AS QUERY_RATE
FROM INFORMATION_SCHEMA.TIDB_HOT_REGIONS_HISTORY
WHERE update_time > DATE_SUB(NOW(), INTERVAL 30 MINUTE)
  AND update_time <= NOW()
  AND `STORE_ID` = "1249"
GROUP BY TABLE_NAME, DB_NAME
ORDER BY QUERY_RATE DESC
LIMIT 10; 

+-----------------------+------------+--------------------+
| DB_NAME               | TABLE_NAME | QUERY_RATE         |
+-----------------------+------------+--------------------+
| RG_SBTEST_32_10000000 | SBTEST1    | 26307.666666666668 |
+-----------------------+------------+--------------------+

Describe the feature you'd like

But I want to know the CPU usage like

+-----------------------+------------+--------------------+---------+
| DB_NAME               | TABLE_NAME | QUERY_RATE         |. CPU
+-----------------------+------------+--------------------+-----------+
| RG_SBTEST_32_10000000 | SBTEST1    | 26307.666666666668 |NAN|
+-----------------------+------------+--------------------+-----------+

actually, we can know the CPU usage after https://github.com/tikv/pd/issues/4042