Enable SQL features selectively

Hello,
given the breadth of the parser, it would be nice if it would be possible to selectively enable features on an opt-in basis.

Let's imagine an application where only a subset of SQL is supported. In this case, the application would need to check for every possible unsupported feature manually (e.g. if I don't support windowing in queries, I would need to check if the `named_window` field in the `Select` gets populated and abort).

It would be interesting, instead, to decide beforehand which feature set is to be supported, so that only "valid" SQL gets parsed and arrives to the application.

Thanks.

该 issue 没有指出文件、测试或入口点。首先定位 parser 的 feature 处理入口点和现有的 parser 测试，然后确定如何选择受支持的 feature 集合，以及如何在不支持的 SQL 到达应用程序之前将其拒绝。

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