fix: Allow public re-export of extern crate import

[ShoyuVanilla]

MCVE:

//- /main.rs crate:main deps:test_crate
use test_crate::foo; // not resolving this!

use foo::Foo;

//- /lib.rs crate:test_crate deps:test_crate2
extern crate test_crate2;

pub use test_crate2 as foo;

//- /lib2.rs crate:test_crate2
pub struct Foo;

It seems that I should exempt min visibility for extern crate, as it seems to be exceptional in rustc 🤔

Originally posted by @ShoyuVanilla in #18390 (comment)

Should fix the regression made by #18390
Thank you @lnicola for pointing out this regression 👍

[ShoyuVanilla]

Oh, these three items should be public visibility 😅
I'll fix this tomorrow

[ShoyuVanilla]

Oh, I found another bug - preexisting before #18390 - related to extern crate that should be dealt with this together.
I'll handle it as well with this

I reviewed this when I was quite tired and there's no such bug 😅
But I found this issue from rustc rust-lang/rust#127909 and addressed this in the comment

[Veykril]

We can't use that here, this draws a dependency edge between the defmap query and the AST causing any AST change to invalidate the def map. We need to derive the relevant info from the item tree somehow

[ShoyuVanilla]

Okay, I'll try different approach