Unquoted identifiers naming rule is incorrect

The naming rule is in https://dev.mysql.com/doc/refman/8.0/en/identifiers.html

The rule for unquoted identifiers is incorrect.
* ASCII: [0-9,a-z,A-Z$_] (basic Latin letters, digits 0-9, dollar, underscore)
* Extended: U+0080 .. U+FFFF

In the following test, we can see that `@` is unpermitted
https://github.com/sqlparser-rs/sqlparser-rs/blob/44727891713114b72546facf21a335606380845a/tests/sqlparser_mysql.rs#L1661

I think we need to fix the unquoted identifiers for MYSQL and HIVE
https://github.com/sqlparser-rs/sqlparser-rs/blob/44727891713114b72546facf21a335606380845a/src/tokenizer.rs#L803-L811

MYSQL
https://github.com/sqlparser-rs/sqlparser-rs/blob/44727891713114b72546facf21a335606380845a/src/dialect/mysql.rs#L28-L41

HIVE
https://github.com/sqlparser-rs/sqlparser-rs/blob/44727891713114b72546facf21a335606380845a/src/dialect/hive.rs#L28-L36

从 tests/sqlparser_mysql.rs:1661 附近的 MySQL 测试开始，然后阅读 src/tokenizer.rs:803-811 中未加引号标识符的逻辑以及 MYSQL 和 HIVE 方言定义。更新两个方言的规则覆盖范围，并添加或调整测试，使 @ 被拒绝，同时接受文档中说明的 ASCII 和扩展范围。

由索引模型根据 Issue 内容生成。