Forbid referencing unknown types for WIT format.

[sviezypan]

Inside the module from which WIT file is generated, we can reference some standard rust type - which is not defined inside module. e.g.

#[golem_rust::create_wit_file]
mod component {
    struct AuctionId {
        auction_id: std::sync::Mutex<u64>
    }
}

This would generate the following content of a WIT file, which is incorrect as mutex is not wit keyword or any defined data type.

record auction-id {
        auction-id: mutex,
}

This ticket is to forbid the ability to write this - make the macro not compile. It would be nice to only allow WIT data types (option, result, list...) and whatever is defined inside the module.