Bug: `SELECT * FROM ( SELECT * FROM APPLICATIONS.SALESFORCE.ACCOUNT) outer` fails to parse in snowflake

I hit a bug where the SQL statement
```sql
SELECT * FROM ( SELECT * FROM APPLICATIONS.SALESFORCE.ACCOUNT) outer
```

failed to parse. This is because `OUTER` is part of the reserved keyword list for table aliases. https://github.com/apache/datafusion-sqlparser-rs/blob/8ccb87a8355858ccb06ffc20484657cd7980d78c/src/keywords.rs#L843-L900

Currently this list is a global but it seems like it should be dialect specific. I'm happy to work on this, but I wanted to know if the project had any opinions on how this list should be maintained at the dialect level.

首先重现 Snowflake 查询并阅读 src/keywords.rs 中链接的范围，尤其要查看 OUTER 是如何分类的。然后检查解析器的方言处理，以确定应如何维护保留关键字列表。完成的标准是报告的查询能够正确解析，同时不会导致其他方言的关键字处理出现回归。

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