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 https://github.com/rust-lang/rust/issues/141301#issuecomment-3390100259 (`#[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 https://github.com/rust-lang/rust/issues/144004#issuecomment-3077725837). </details> r? GuillaumeGomez