fix: Implement missing logics in exported_private_dependencies lint

[ShoyuVanilla]

Fixes some cases of #71043

[rustbot]

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[ShoyuVanilla]

r? compiler

[petrochenkov]

rustc_privacy is very unlikely to be the right place to process use and extern crate items.
I'm now back to reviews and was going to review this ~next week.

[ShoyuVanilla]

rustc_privacy is very unlikely to be the right place to process use and extern crate items.

Actually, I'm preparing another PR that fixes #119428 once and for all with some changes in ast path lowering and nameres resolves.
Should use and extern crate items be handled in rustc_resolve? Then I'll include them in that PR in proper locations.

[petrochenkov]

Should use and extern crate items be handled in rustc_resolve?

Yes, most likely.
In general all privacy/visibility checks are split into two parts - one in rustc_resolve for everything that doesn't require type checking, and rustc_privacy for things that do require type checking results.

See, for example, the effective_visibilities table that is build in 2 steps, or just regular privacy check.

[petrochenkov]

I started reviewing this and I was sure that check_private_dep_leaks_only shouldn't exist, and the visitor should just always visit the impl's type and trait.
So I started figuring out why they weren't visited, and implemented a better solution (#138317) in the process.

Technically, the regular type privacy lints (not private dep leaks) should be reported there as well, it was just skipped due to many false positives.

Closing in favor of #138317.