support parsing mysql 8 check related DDL statement #4089

[WillsonYip]

fix issue #4089

增加mysql 8 check语句的支持, 包括下面：

CREATE TABLE `t12` (
	`c1` int DEFAULT NULL,
	`c2` int DEFAULT NULL,
	`c3` int DEFAULT NULL,
	CONSTRAINT `c12_positive` CHECK (`c2` > 0) NOT ENFORCED,
	CONSTRAINT `c21_nonzero` CHECK (`c1` <> 0),
	CONSTRAINT `t12_chk_1` CHECK (`c1` <> `c2`),
	CONSTRAINT `t12_chk_2` CHECK (`c1` > 10),
	CONSTRAINT `t12_chk_3` CHECK (`c3` < 100),
	CONSTRAINT `t12_chk_4` CHECK (`c1` > `c3`)
) ENGINE = InnoDB CHARSET = utf8mb4 COLLATE = utf8mb4_0900_ai_ci;

# 新增check 约束
ALTER TABLE t1 ADD CONSTRAINT chk1 CHECK((a>1));
ALTER TABLE t1 ADD CONSTRAINT chk1 CHECK((a>1)) NOT ENFORCED; 

# 删除check 约束
ALTER TABLE t1 DROP CONSTRAINT t1_check ;

# 让check约束不生效
alter table t1 ALTER CHECK  t1_check  ENFORCED;
alter table t1 ALTER CHECK  t1_check  NOT ENFORCED;

修改说明:

1. 修改MySqlCreateTableParser，使得支持create table语句中的 [CONSTRAINT [symbol]] CHECK (expr) [[NOT] ENFORCED]语法

2. 新增MysqlAlterTableAlterCheck 类来识别 ALTER TABLE tbl_name ALTER {CHECK | CONSTRAINT} symbol [NOT] ENFORCED 语句

3. 调整MySqlStatementParser.java代码顺序，使得可以支持 ALTER TABLE tbl_name ADD [CONSTRAINT [symbol]] CHECK (expr) [[NOT] ENFORCED] 语句

4. ALTER TABLE tbl_name DROP {CHECK | CONSTRAINT} symbol 这个不需要修改，已经支持了

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[wenshao]

请补上testcase

[wenshao]

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