executor/inspect: refactor current-load diagnosis rule to node-check (#15860)

[sre-bot]

cherry-pick #15860 to release-4.0

---

What problem does this PR solve?

Before this PR, TiDB has a current-load diagnosis rule, but it can only diagnose for the current time load.

What is changed and how it works?

This PR change current-load to node-load diagnose rule, since it uses the metrics data, so it can diagnose at any time.

This diagnose rule depends on below metric tables:

• node_load1
• node_load5
• node_load15
• node_virtual_cpus
• node_memory_usage
• node_memory_swap_used
• node_disk_usage

eg:

>select /*+ time_range("2020-03-30 16:22:04", "2020-03-30 16:50:04") */ * from inspection_result where rule='node-load'
+-----------+----------------------+------+-------------------+-------+-----------+----------+-------------------------------------------------------+
| RULE      | ITEM                 | TYPE | INSTANCE          | VALUE | REFERENCE | SEVERITY | DETAILS                                               |
+-----------+----------------------+------+-------------------+-------+-----------+----------+-------------------------------------------------------+
| node-load | cpu-load1            | node | 172.16.5.40:19110 | 41.1  | < 28.0    | warning  | cpu-load1 should less than (cpu_logical_cores * 0.7)  |
| node-load | cpu-load15           | node | 172.16.5.40:19110 | 36.2  | < 28.0    | warning  | cpu-load15 should less than (cpu_logical_cores * 0.7) |
| node-load | cpu-load5            | node | 172.16.5.40:19110 | 39.5  | < 28.0    | warning  | cpu-load5 should less than (cpu_logical_cores * 0.7)  |
| node-load | disk-usage           | node | 172.16.5.40:19110 | 92.4% | < 70%     | warning  | the disk-usage of /dev/sda3 is too high               |
| node-load | disk-usage           | node | 172.16.5.40:19110 | 95.6% | < 70%     | warning  | the disk-usage of /dev/nvme0n1 is too high            |
| node-load | disk-usage           | node | 172.16.5.40:19110 | 99.8% | < 70%     | warning  | the disk-usage of /dev/sda1 is too high               |
| node-load | swap-memory-used     | node | 172.16.5.40:19110 | 586.0 | 0         | warning  |                                                       |
| node-load | virtual-memory-usage | node | 172.16.5.40:19110 | 83.9% | < 70%     | warning  | the memory-usage of 172.16.5.40:19110 is too high     |
+-----------+----------------------+------+-------------------+-------+-----------+----------+-------------------------------------------------------+

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:

Check List

Tests

• Unit test
• Manual test (add detailed scripts or steps below)

Side effects

Release note

• refactor current-load diagnosis rule to node-check

[sre-bot]

/run-all-tests

[crazycs520]

/run-all-tests

[lonng]

LGTM

[AilinKid]

LGTM