def: support --env and --wrapped

[WindSoilder]

I plan to add parser keywords as AstNode variants. I'm not sure if it's a right direction, so here is a small pr about def parsing, it adds env: bool and wrapped: bool as part of a def ast node.

Then these information can be used after parsing.

[ysthakur]

Thanks for the quick changes! Not too familiar with the new parser but this looks simple enough. Let's go for it

[kubouch]

About these, I was thinking we could first implement general-purpose flag parsing logic for custom commands and then reuse that for --env and --wrapped. But this is fine for now.

One more thing to keep in mind when adding fields to the AstNode enums is to keep track of the enum size. If one enum variant grows too large, we could optimize it, e.g., by using a separate storage for it with a new Id type, like BlockId or PipelineId. This is just an optimization, not necessary to do now.