fix: Calculate the privacy of dependencies wrt current local crate

[ShoyuVanilla]

Partially mitigates #119428

This PR addresses most aspects of the issue, except for the following cases:

• When the same crate is exported through multiple routes in the dependency graph, requiring us to determine its pub-priv status based on the import path.

For example, consider the following cases:

rust/tests/ui/privacy/pub-priv-dep/shared_direct_private.rs

Lines 26 to 33 in 15469f8

	// FIXME: Should this trigger?
	//
	// One could make an argument that I said I want "reexport" to be public, and
	// since "reexport" says "shared_direct_private" is public, then it should
	// transitively be public for me. However, as written, this is explicitly
	// referring to a dependency that is marked "private", which I think is
	// confusing.
	pub fn leaks_priv() -> shared::Shared {

rust/tests/ui/privacy/pub-priv-dep/diamond_deps.rs

Lines 32 to 33 in 15469f8

	// FIXME: This should trigger.
	pub fn leaks_priv() -> diamond_priv_dep::Shared {

Resolving the remaining issue likely requires modifying the path lowering logic. I plan to work on that in a follow-up PR—assuming, of course, that this one gets merged first! 😅

P.S. I'd also appreciate a review on #134176 😊

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[ShoyuVanilla]

According to the diagram commented below, I think that this is the original intention of this test

[bors]

☔ The latest upstream changes (presumably #137446) made this pull request unmergeable. Please resolve the merge conflicts.

[ShoyuVanilla]

Oh, this overlaps a bit with #135501. I'll resolve the conflicts.