Auto merge of #148660 - fmease:cross-crate-cfg, r=GuillaumeGomez

Encode cfg trace, not its early counterpart to fix cross-crate `doc(auto_cfg)`

Fixes rust-lang/rust#141301.

<details><summary>Rambling about <code>target_feature</code> which I didn't touch here</summary>

Regarding rust-lang/rust#141301 (comment) (`#[target_feature(enable = …)]` on inlined cross-crate re-exports), it has the same underlying cause (namely, we neither encode `target_feature` nor `AttributeKind::TargetFeature` in the crate metadata). However, I didn't make that change because I first want to experiment with querying `TyCtxt::codegen_fn_attrs` in rustdoc instead which already works cross-crate (and also use to it for reconstructing `no_mangle`, `export_name`, `link_section` to avoid encoding these attributes unnecessarily (basically reverting rust-lang/rust#144050) as suggested in rust-lang/rust#144004 (comment)).

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r? GuillaumeGomez

Author: bors