chore(planner): Add statistics info in explain result

[leiysky]

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Summary

Example:

mysql> explain select number+1 from numbers(10);
+----------------------------------------------------------+
| explain                                                  |
+----------------------------------------------------------+
| Project                                                  |
| ├── columns: [1]                                         |
| └── EvalScalar                                           |
|     ├── expressions: [+(numbers.number, 1)]              |
|     └── TableScan                                        |
|         ├── table: default.system.numbers                |
|         ├── read rows: 10                                |
|         ├── read bytes: 80                               |
|         ├── partitions total: 1                          |
|         ├── partitions scanned: 1                        |
|         └── push downs: [filters: [], limit: NONE]       |
+----------------------------------------------------------+
11 rows in set (0.02 sec)
Read 0 rows, 0.00 B in 0.005 sec., 0 rows/sec., 0.00 B/sec.

Close #7350

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1 Ignored Deployment

Name	Status	Preview	Updated
databend	⬜️ Ignored (Inspect)		Aug 30, 2022 at 3:59PM (UTC)

[BohuTANG]

Many logic tests failed(due to the explain format):
https://github.com/datafuselabs/databend/runs/8093212379?check_suite_focus=true#step:4:1244

[BohuTANG]

👍

[BohuTANG]

Please document the EXPLAIN statement in https://databend.rs/doc/reference/sql/explain-commands, thanks @soyeric128