Report the unsafe_attr_outside_unsafe lint at the closest node

[Urgau]

This PR have AstValidation track a linting node id and then uses it when reporting the unsafe_attr_outside_unsafe lint, so that instead of being bound at the crate-root, #[allow] of the lint works at any node.

Fixes #140602
r? @jieyouxu

[jieyouxu]

Thanks! One nit, but r=me otherwise

[jieyouxu]

@rustbot author

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[jieyouxu]

Don't know if we want to backport this to beta, it's in stable ever since this lint was implemented I think

[jieyouxu]

I'll nominate this for beta-backport discussion at least.

---

This PR fixes a bug reported in #140602, where it wasn't possible to #[allow(unsafe_attr_outside_unsafe)] in scopes within crate root, e.g. the following will error and not compile

#![deny(unsafe_attr_outside_unsafe)]

#[allow(unsafe_attr_outside_unsafe)]
mod generated {
    #[no_mangle]
    fn _generated_foo() {}
}

This was broken since the unsafe_attr_outside_unsafe lint was introduced (also present on stable since it was stabilized). EDIT: confirmed with a bisection.

@rustbot label: +beta-nominated

[Urgau]

@bors r=@jieyouxu rollup

[bors]

📌 Commit f4e1ec1 has been approved by jieyouxu

It is now in the queue for this repository.

[jieyouxu]

This was discussed in today's compiler triage meeting. We considered the beta backport nomination but decided to decline this beta backport.

The beta backport was considered but rejected because:

• It's very late into the release cycle.
• It has been broken ever since the lint was stabilized, but we only received one bug report.

@rustbot label: -beta-nominated