Rollup merge of #153630 - arferreira:fix-doc-hidden-reexport-diagnostic-path, r=jackh726

Deprioritize doc(hidden) re-exports in diagnostic paths

Fixes rust-lang/rust#153477.

This is the other half of rust-lang/rust#99698, which fixed the case where the *parent module* is `#[doc(hidden)]` but left the case where the re-export itself is `#[doc(hidden)]` as a FIXME (with a tracking test in `dont-suggest-doc-hidden-variant-for-enum/hidden-child.rs`).

The problem: when a crate does `#[doc(hidden)] pub use core::error::Error`, diagnostics pick up the hidden re-export path instead of the canonical one. For example, `snafu::Error` instead of `std::error::Error`.

Two changes:

In `visible_parent_map`, the `add_child` closure now checks whether the re-export itself is `#[doc(hidden)]` via `reexport_chain` and sends it to `fallback_map`, same treatment as doc-hidden parents and underscore re-exports.

`should_encode_attrs` now returns `true` for `DefKind::Use`. Without this, `#[doc(hidden)]` on `use` items was never written to crate metadata, so `is_doc_hidden` always returned `false` cross-crate. This was the actual root cause, the check in `visible_parent_map` alone isn't enough if the attribute isn't in the metadata.

The existing FIXME test now serves as the regression test. The `.stderr` goes from suggesting `hidden_child::__private::Some(1i32)` to just `Some(1i32)`.

cc @eggyal