feat(planner): support explain syntax

[b41sh]

I hereby agree to the terms of the CLA available at: https://databend.rs/dev/policies/cla/

Summary

Support explain syntax.
Inspired by forma, use pretty to output the formatted SQL

#7063

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1 Ignored Deployment

Name	Status	Preview	Updated
databend	⬜️ Ignored (Inspect)		Aug 17, 2022 at 1:27AM (UTC)

[leiysky]

I think the new pretty function is actually a reimplementation of Display of AST, is it possible to replace the current implementation of Display with pretty?

[b41sh]

I think the new pretty function is actually a reimplementation of Display of AST, is it possible to replace the current implementation of Display with pretty?

yes, we can use pretty to replace Display.

[BohuTANG]

yes, we can use pretty to replace Display.

Will do it in this PR or not?

[b41sh]

yes, we can use pretty to replace Display.

Will do it in this PR or not?

In a new PR, a lot work need to do.

[BohuTANG]

Following failed statements:
---------------------------------------------
Runner: mysql
ErrorType: statement query get result not equal to expected
Message: 
 Expected:
SELECT
    1,
    'ab',
    [1, 2, 3],
    (1, 'a')                             
 Actual:
EXPLAIN SYNTAX SELECT 1, 'ab', [1, 2, 3], (1, 'a')                              
 Statement:
Parsed Statement
    at_line: 71,
    s_type: Statement: query, type: T, query_type: T, retry: False,
    suite_name: standalone/04_0002_explain_v2,
    text:
        explain syntax explain syntax select 1, 'ab', [1,2,3], (1, 'a');
    results: [(<re.Match object; span=(0, 4), match='----'>, 79, "SELECT\n    1,\n    'ab',\n    [1, 2, 3],\n    (1, 'a')")],
    runs_on: {'mysql'},
 Start Line: 79, Result Label: 

[BohuTANG]

cc @soyeric128 for explain syntax statement documentation.